diff --git a/example/05-explain-crontabs.php b/example/05-explain-crontabs.php
new file mode 100644
index 0000000..7652a0e
--- /dev/null
+++ b/example/05-explain-crontabs.php
@@ -0,0 +1,35 @@
+<?php
+use GT\Cron\CrontabParser;
+use GT\Cron\CronExplainer;
+
+chdir(dirname(__DIR__));
+require "vendor/autoload.php";
+
+$crontab = <<<'CRON'
+# Explain a few different schedule styles.
+@DAILY printf 'Daily backup.\n'
+*/10s * * * * printf 'Heartbeat tick.\n'
+0 9 * * MON,WED,FRI printf 'Team summary.\n'
+05 01 * MAY SUN#2 printf 'May maintenance window.\n'
+CRON;
+
+$parser = new CrontabParser();
+$explainer = new CronExplainer();
+
+echo "Crontab:" . PHP_EOL;
+echo $crontab . PHP_EOL . PHP_EOL;
+echo "Explanations:" . PHP_EOL;
+
+foreach(explode("\n", $crontab) as $line) {
+	$line = trim($line);
+	if($line === "" || $line[0] === "#") {
+		continue;
+	}
+
+	[$expression, $command] = $parser->parseLine($line);
+	echo $expression
+		. " " . $command
+		. PHP_EOL . "  -> "
+		. $explainer->explain($expression)
+		. PHP_EOL;
+}
diff --git a/example/README.md b/example/README.md
index af97866..b92d3a5 100644
--- a/example/README.md
+++ b/example/README.md
@@ -7,6 +7,7 @@ php example/01-run-due-jobs.php
 php example/02-next-job.php
 php example/03-nickname-expressions.php
 php example/04-custom-expression-factory.php
+php example/05-explain-crontabs.php
 ```
 
 Each script embeds its own crontab string so you can read the schedule and the code together.
diff --git a/src/Cli/RunCommand.php b/src/Cli/RunCommand.php
index ae2fe07..3db12c1 100644
--- a/src/Cli/RunCommand.php
+++ b/src/Cli/RunCommand.php
@@ -8,8 +8,11 @@
 use Gt\Cli\Parameter\Parameter;
 use Gt\Cli\Stream;
 use GT\Cron\CronException;
+use GT\Cron\CronExplainer;
 use GT\Cron\CrontabNotFoundException;
+use GT\Cron\CrontabParser;
 use GT\Cron\FunctionExecutionException;
+use GT\Cron\ParseException;
 use GT\Cron\RunnerFactory;
 use GT\Cron\ScriptExecutionException;
 
@@ -45,6 +48,11 @@ public function run(?ArgumentValueList $arguments = null):int {
 			exit(0);
 		}
 
+		if($arguments->contains("explain")) {
+			$this->explainCrontab(file_get_contents($filePath));
+			return 0;
+		}
+
 		$runner->setRunCallback([$this, "cronRunStep"]);
 
 		if($arguments->contains("now")) {
@@ -139,6 +147,28 @@ protected function displayCommandName(string $command):string {
 		return basename(str_replace("\\", "/", $script));
 	}
 
+	protected function explainCrontab(string $contents):void {
+		$parser = new CrontabParser();
+		$explainer = new CronExplainer();
+
+		foreach(explode("\n", $contents) as $line) {
+			$line = trim($line);
+			if($line === "" || $line[0] === "#") {
+				continue;
+			}
+
+			try {
+				[$crontab, $command] = $parser->parseLine($line);
+				$explanation = $explainer->explain($crontab);
+			}
+			catch(ParseException) {
+				throw new ParseException("Invalid syntax: $line");
+			}
+
+			$this->writeLine("$crontab $command\t\t$explanation");
+		}
+	}
+
 	public function getName():string {
 		return "run";
 	}
@@ -179,6 +209,12 @@ public function getOptionalParameterList():array {
 				null,
 				"Check the syntax of the crontab file without running anything."
 			),
+			new Parameter(
+				false,
+				"explain",
+				null,
+				"List the cron jobs and explain when each one will run."
+			),
 			new Parameter(
 				true,
 				"now",
diff --git a/src/CronExplainer.php b/src/CronExplainer.php
new file mode 100644
index 0000000..f442496
--- /dev/null
+++ b/src/CronExplainer.php
@@ -0,0 +1,334 @@
+<?php
+namespace GT\Cron;
+
+use InvalidArgumentException;
+
+/** @SuppressWarnings(PHPMD.ExcessiveClassComplexity) */
+class CronExplainer {
+	/** @var array<string,string> */
+	private const NICKNAME_MAP = [
+		"@yearly" => "0 0 1 1 *",
+		"@annually" => "0 0 1 1 *",
+		"@monthly" => "0 0 1 * *",
+		"@weekly" => "0 0 * * 0",
+		"@daily" => "0 0 * * *",
+		"@hourly" => "0 * * * *",
+	];
+
+	/** @var array<int|string,string> */
+	private const WEEKDAY_NAME_MAP = [
+		"0" => "Sunday",
+		"7" => "Sunday",
+		"SUN" => "Sunday",
+		"1" => "Monday",
+		"MON" => "Monday",
+		"2" => "Tuesday",
+		"TUE" => "Tuesday",
+		"3" => "Wednesday",
+		"WED" => "Wednesday",
+		"4" => "Thursday",
+		"THU" => "Thursday",
+		"5" => "Friday",
+		"FRI" => "Friday",
+		"6" => "Saturday",
+		"SAT" => "Saturday",
+	];
+
+	/** @var array<int,string> */
+	private const ORDINAL_MAP = [
+		1 => "first",
+		2 => "second",
+		3 => "third",
+		4 => "fourth",
+		5 => "fifth",
+	];
+
+	/** @var array<int|string,string> */
+	private const MONTH_NAME_MAP = [
+		"1" => "January",
+		"JAN" => "January",
+		"2" => "February",
+		"FEB" => "February",
+		"3" => "March",
+		"MAR" => "March",
+		"4" => "April",
+		"APR" => "April",
+		"5" => "May",
+		"MAY" => "May",
+		"6" => "June",
+		"JUN" => "June",
+		"7" => "July",
+		"JUL" => "July",
+		"8" => "August",
+		"AUG" => "August",
+		"9" => "September",
+		"SEP" => "September",
+		"10" => "October",
+		"OCT" => "October",
+		"11" => "November",
+		"NOV" => "November",
+		"12" => "December",
+		"DEC" => "December",
+	];
+
+	public function explain(string $expression):string {
+		$expression = trim($expression);
+		$expression = self::NICKNAME_MAP[strtolower($expression)]
+			?? $expression;
+		new CronExpression($expression);
+		$parts = preg_split("/\s+/", $expression);
+
+		if(!$parts || count($parts) !== 5) {
+			throw new InvalidArgumentException("$expression is not a valid CRON expression");
+		}
+
+		[$minute, $hour, $dayOfMonth, $month, $dayOfWeek] = $parts;
+
+		if($this->isEveryHour($minute, $hour, $dayOfMonth, $month, $dayOfWeek)) {
+			return "Every hour";
+		}
+
+		$phraseList = [$this->explainTime($minute, $hour)];
+		$dayPhrase = $this->explainDay($dayOfMonth, $dayOfWeek, $month);
+		if($dayPhrase) {
+			$phraseList []= $dayPhrase;
+		}
+
+		return implode(", ", $phraseList);
+	}
+
+	private function isEveryHour(
+		string $minute,
+		string $hour,
+		string $dayOfMonth,
+		string $month,
+		string $dayOfWeek
+	):bool {
+		return $minute === "0"
+			&& $hour === "*"
+			&& $dayOfMonth === "*"
+			&& $month === "*"
+			&& $dayOfWeek === "*";
+	}
+
+	private function explainTime(string $minute, string $hour):string {
+		if(str_ends_with(strtolower($minute), "s") && $hour === "*") {
+			return $this->explainSecondTime($minute);
+		}
+
+		$wildcardHourTime = $this->explainWildcardHourTime($minute, $hour);
+		if(!is_null($wildcardHourTime)) {
+			return $wildcardHourTime;
+		}
+
+		return $this->explainFixedHourTime($minute, $hour);
+	}
+
+	private function explainSecondTime(string $minute):string {
+		$second = substr($minute, 0, -1);
+		if(str_starts_with($second, "*/")) {
+			return "Every " . substr($second, 2) . " seconds";
+		}
+
+		if($this->isInteger($second)) {
+			return "At " . (int)$second . " seconds past every minute";
+		}
+
+		return "At second $second of every minute";
+	}
+
+	private function explainWildcardHourTime(
+		string $minute,
+		string $hour
+	):?string {
+		if($hour !== "*") {
+			return null;
+		}
+
+		if($minute === "*") {
+			return "Every minute";
+		}
+
+		if(str_starts_with($minute, "*/")) {
+			return "Every " . substr($minute, 2) . " minutes";
+		}
+
+		if($this->isInteger($minute)) {
+			return "At " . (int)$minute . " minutes past every hour";
+		}
+
+		return null;
+	}
+
+	private function explainFixedHourTime(string $minute, string $hour):string {
+		if($this->isInteger($minute) && $this->isInteger($hour)) {
+			return "At " . $this->formatTime((int)$hour, (int)$minute);
+		}
+
+		return "At minute $minute of hour $hour";
+	}
+
+	private function explainDay(
+		string $dayOfMonth,
+		string $dayOfWeek,
+		string $month
+	):?string {
+		$monthPhrase = $this->formatMonth($month);
+
+		if($dayOfMonth === "*" && $dayOfWeek === "*") {
+			return $monthPhrase ? "only in $monthPhrase" : null;
+		}
+
+		if($dayOfMonth === "*" && str_contains($dayOfWeek, "#")) {
+			return $this->explainNthDayOfWeek($dayOfWeek, $monthPhrase);
+		}
+
+		if($dayOfMonth === "*") {
+			return $this->explainDayOfWeek($dayOfWeek, $monthPhrase);
+		}
+
+		if($dayOfWeek === "*") {
+			return $this->formatDayOfMonth($dayOfMonth, $monthPhrase);
+		}
+
+		return $this->formatDayOfMonth($dayOfMonth, $monthPhrase)
+			. " or on " . $this->formatDayOfWeek($dayOfWeek);
+	}
+
+	private function explainNthDayOfWeek(
+		string $dayOfWeek,
+		?string $monthPhrase
+	):string {
+		$phrase = "on " . $this->formatNthDayOfWeekList($dayOfWeek);
+		return $monthPhrase ? "$phrase in $monthPhrase" : $phrase;
+	}
+
+	private function explainDayOfWeek(
+		string $dayOfWeek,
+		?string $monthPhrase
+	):string {
+		$phrase = "only on " . $this->formatDayOfWeek($dayOfWeek);
+		return $monthPhrase ? "$phrase in $monthPhrase" : $phrase;
+	}
+
+	private function formatTime(int $hour, int $minute):string {
+		$suffix = $hour >= 12 ? "PM" : "AM";
+		$hour12 = $hour % 12;
+		if($hour12 === 0) {
+			$hour12 = 12;
+		}
+
+		return sprintf("%02d:%02d %s", $hour12, $minute, $suffix);
+	}
+
+	private function formatNthDayOfWeek(string $dayOfWeek):string {
+		[$day, $nth] = explode("#", strtoupper($dayOfWeek), 2);
+		$ordinal = self::ORDINAL_MAP[(int)$nth] ?? "{$nth}th";
+		return $ordinal . " " . $this->formatDayOfWeek($day);
+	}
+
+	private function formatNthDayOfWeekList(string $dayOfWeek):string {
+		$phraseList = [];
+
+		foreach(explode(",", $dayOfWeek) as $part) {
+			if(str_contains($part, "#")) {
+				$phraseList []= "the " . $this->formatNthDayOfWeek($part)
+					. " of the month";
+				continue;
+			}
+
+			$phraseList []= $this->formatDayOfWeek($part);
+		}
+
+		return $this->formatList($phraseList);
+	}
+
+	private function formatDayOfWeek(string $dayOfWeek):string {
+		$dayOfWeekList = array_map(
+			function(string $part):string {
+				return $this->formatDayOfWeekPart($part);
+			},
+			explode(",", $dayOfWeek)
+		);
+
+		return $this->formatList($dayOfWeekList);
+	}
+
+	private function formatDayOfWeekPart(string $dayOfWeek):string {
+		$dayOfWeek = strtoupper($dayOfWeek);
+		if(str_contains($dayOfWeek, "-")) {
+			[$start, $end] = explode("-", $dayOfWeek, 2);
+			return $this->formatDayOfWeekPart($start)
+				. " through " . $this->formatDayOfWeekPart($end);
+		}
+
+		return self::WEEKDAY_NAME_MAP[$dayOfWeek] ?? $dayOfWeek;
+	}
+
+	private function formatDayOfMonth(
+		string $dayOfMonth,
+		?string $monthPhrase
+	):string {
+		if($monthPhrase && $this->isInteger($dayOfMonth)) {
+			return "on " . $this->formatMonthDay((int)$dayOfMonth)
+				. " " . $monthPhrase;
+		}
+
+		$phrase = "on day $dayOfMonth of the month";
+		return $monthPhrase ? "$phrase in $monthPhrase" : $phrase;
+	}
+
+	private function formatMonthDay(int $day):string {
+		$suffix = "th";
+		if($day % 100 < 11 || $day % 100 > 13) {
+			$suffix = match($day % 10) {
+				1 => "st",
+				2 => "nd",
+				3 => "rd",
+				default => "th",
+			};
+		}
+
+		return $day . $suffix;
+	}
+
+	private function formatMonth(string $month):?string {
+		if($month === "*") {
+			return null;
+		}
+
+		$monthList = array_map(
+			function(string $part):string {
+				return $this->formatMonthPart($part);
+			},
+			explode(",", $month)
+		);
+
+		return $this->formatList($monthList);
+	}
+
+	private function formatMonthPart(string $month):string {
+		$month = strtoupper($month);
+		if(str_contains($month, "-")) {
+			[$start, $end] = explode("-", $month, 2);
+			return $this->formatMonthPart($start)
+				. " through " . $this->formatMonthPart($end);
+		}
+
+		return self::MONTH_NAME_MAP[$month] ?? $month;
+	}
+
+	/** @param array<string> $partList */
+	private function formatList(array $partList):string {
+		if(count($partList) <= 1) {
+			return $partList[0] ?? "";
+		}
+
+		$last = array_pop($partList);
+		return implode(", ", $partList) . " and " . $last;
+	}
+
+	private function isInteger(string $value):bool {
+		return (bool)preg_match("/^\d+$/", $value);
+	}
+}
diff --git a/src/CronExpression.php b/src/CronExpression.php
index b62a1fe..ff6dfd1 100644
--- a/src/CronExpression.php
+++ b/src/CronExpression.php
@@ -58,6 +58,8 @@ class CronExpression implements Expression {
 	private array $monthSet;
 	/** @var array<int,bool> */
 	private array $dayOfWeekSet;
+	/** @var array<int,array<int,bool>> */
+	private array $nthDayOfWeekSet = [];
 
 	private bool $dayOfMonthWildcard;
 	private bool $dayOfWeekWildcard;
@@ -76,13 +78,11 @@ public function __construct(string $expression) {
 		$this->hourSet = $this->fieldParser->parseField($parts[1], 0, 23);
 		[$this->dayOfMonthSet, $this->dayOfMonthWildcard] = $this->fieldParser->parseFieldWithWildcard($parts[2], 1, 31);
 		$this->monthSet = $this->fieldParser->parseField($parts[3], 1, 12, self::MONTH_MAP);
-		[$this->dayOfWeekSet, $this->dayOfWeekWildcard] = $this->fieldParser->parseFieldWithWildcard(
-			$parts[4],
-			0,
-			7,
-			self::WEEKDAY_MAP,
-			true
-		);
+		[
+			$this->dayOfWeekSet,
+			$this->dayOfWeekWildcard,
+			$this->nthDayOfWeekSet
+		] = $this->parseDayOfWeekField($parts[4]);
 	}
 
 	public function isDue(DateTime $now):bool {
@@ -117,7 +117,7 @@ public function getNextRunDate(?DateTime $now = null):DateTime {
 
 	private function expandNickname(string $expression):string {
 		$expression = trim($expression);
-		return self::NICKNAME_MAP[$expression] ?? $expression;
+		return self::NICKNAME_MAP[strtolower($expression)] ?? $expression;
 	}
 
 	private function matches(DateTime $candidate):bool {
@@ -163,7 +163,8 @@ private function matchesSecond(int $second):bool {
 
 	private function matchesDay(int $dayOfMonth, int $dayOfWeek):bool {
 		$dayOfMonthMatches = isset($this->dayOfMonthSet[$dayOfMonth]);
-		$dayOfWeekMatches = isset($this->dayOfWeekSet[$dayOfWeek]);
+		$dayOfWeekMatches = isset($this->dayOfWeekSet[$dayOfWeek])
+			|| $this->matchesNthDayOfWeek($dayOfMonth, $dayOfWeek);
 
 		if($this->dayOfMonthWildcard && $this->dayOfWeekWildcard) {
 			return true;
@@ -180,6 +181,85 @@ private function matchesDay(int $dayOfMonth, int $dayOfWeek):bool {
 		return $dayOfMonthMatches || $dayOfWeekMatches;
 	}
 
+	/**
+	 * @return array{0:array<int,bool>,1:bool,2:array<int,array<int,bool>>}
+	 */
+	private function parseDayOfWeekField(string $field):array {
+		$field = trim($field);
+		$isWildcard = $field === "*" || $field === "?";
+		$standardSegmentList = [];
+		$nthDayOfWeekSet = [];
+
+		foreach(explode(",", $field) as $segment) {
+			$segment = trim($segment);
+			if($segment === "") {
+				throw new InvalidArgumentException("Invalid CRON field value $field");
+			}
+
+			if(!str_contains($segment, "#")) {
+				$standardSegmentList []= $segment;
+				continue;
+			}
+
+			[$dayOfWeek, $nth] = $this->parseNthDayOfWeekSegment($segment);
+			$nthDayOfWeekSet[$dayOfWeek][$nth] = true;
+		}
+
+		$dayOfWeekSet = [];
+		if($standardSegmentList) {
+			[$dayOfWeekSet] = $this->fieldParser->parseFieldWithWildcard(
+				implode(",", $standardSegmentList),
+				0,
+				7,
+				self::WEEKDAY_MAP,
+				true
+			);
+		}
+
+		return [$dayOfWeekSet, $isWildcard, $nthDayOfWeekSet];
+	}
+
+	/** @return array{0:int,1:int} */
+	private function parseNthDayOfWeekSegment(string $segment):array {
+		[$dayOfWeekPart, $nthPart] = explode("#", strtoupper($segment), 2);
+		if($dayOfWeekPart === ""
+		|| $nthPart === ""
+		|| str_contains($nthPart, "#")
+		|| !ctype_digit($nthPart)) {
+			throw new InvalidArgumentException("Invalid CRON field value $segment");
+		}
+
+		$nth = (int)$nthPart;
+		if($nth < 1 || $nth > 5) {
+			throw new InvalidArgumentException("Invalid CRON field value $segment");
+		}
+
+		$dayOfWeekSet = $this->fieldParser->parseField(
+			$dayOfWeekPart,
+			0,
+			7,
+			self::WEEKDAY_MAP,
+			true
+		);
+		if(count($dayOfWeekSet) !== 1) {
+			throw new InvalidArgumentException("Invalid CRON field value $segment");
+		}
+
+		return [array_key_first($dayOfWeekSet), $nth];
+	}
+
+	private function matchesNthDayOfWeek(
+		int $dayOfMonth,
+		int $dayOfWeek
+	):bool {
+		if(!isset($this->nthDayOfWeekSet[$dayOfWeek])) {
+			return false;
+		}
+
+		$nth = intdiv($dayOfMonth - 1, 7) + 1;
+		return isset($this->nthDayOfWeekSet[$dayOfWeek][$nth]);
+	}
+
 	private function getMaxLookaheadSteps():int {
 		if($this->hasSecondPrecision()) {
 			return self::MAX_LOOKAHEAD_MINUTES * self::SECONDS_PER_MINUTE;
diff --git a/test/phpunit/Command/RunCommandTest.php b/test/phpunit/Command/RunCommandTest.php
index e7d2ee1..5c0069b 100644
--- a/test/phpunit/Command/RunCommandTest.php
+++ b/test/phpunit/Command/RunCommandTest.php
@@ -137,6 +137,71 @@ public function testRunInvalidSyntax() {
 		);
 	}
 
+	public function testExplain():void {
+		$cronContents = <<<CRON
+0 0 * * FRI /backup
+0 * * * * /clean-cache
+05 01 * * SUN#1 /first-sunday
+CRON;
+		$this->writeCronContents($cronContents);
+		$stream = $this->getStream();
+		chdir($this->projectDirectory);
+
+		$args = new ArgumentValueList();
+		$args->set("explain");
+		$command = new RunCommand();
+		$command->setStream($stream);
+		$command->run($args);
+
+		$output = $this->getFullOutput($stream);
+		self::assertStringContainsString(
+			"0 0 * * FRI /backup\t\tAt 12:00 AM, only on Friday",
+			$output
+		);
+		self::assertStringContainsString(
+			"0 * * * * /clean-cache\t\tEvery hour",
+			$output
+		);
+		self::assertStringContainsString(
+			"05 01 * * SUN#1 /first-sunday\t\tAt 01:05 AM, on the first Sunday of the month",
+			$output
+		);
+	}
+
+	public function testExplainSkipsCommentsAndBlankLinesAndSupportsAliases():void {
+		$cronContents = <<<'CRON'
+# This line should be ignored
+
+@DAILY /backup
+*/10s * * * * /tick
+
+CRON;
+		$this->writeCronContents($cronContents);
+		$stream = $this->getStream();
+		chdir($this->projectDirectory);
+
+		$args = new ArgumentValueList();
+		$args->set("explain");
+		$command = new RunCommand();
+		$command->setStream($stream);
+		$command->run($args);
+
+		$output = $this->getFullOutput($stream);
+		self::assertStringContainsString(
+			"@DAILY /backup\t\tAt 12:00 AM",
+			$output
+		);
+		self::assertStringContainsString(
+			"*/10s * * * * /tick\t\tEvery 10 seconds",
+			$output
+		);
+		self::assertStringNotContainsString(
+			"# This line should be ignored",
+			$output
+		);
+		self::assertSame(2, substr_count($output, PHP_EOL));
+	}
+
 	public function testRunNowFunction() {
 		$cronContents = <<<CRON
 * * * * * \GT\Cron\Test\Helper\ExampleClass::doSomething
diff --git a/test/phpunit/CronExplainerTest.php b/test/phpunit/CronExplainerTest.php
new file mode 100644
index 0000000..f1a4687
--- /dev/null
+++ b/test/phpunit/CronExplainerTest.php
@@ -0,0 +1,276 @@
+<?php
+namespace GT\Cron\Test;
+
+use GT\Cron\CronExplainer;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+class CronExplainerTest extends TestCase {
+	/** @dataProvider simpleScheduleData */
+	public function testSimpleSchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function simpleScheduleData():array {
+		return [
+			"every minute" => ["* * * * *", "Every minute"],
+			"every ten minutes" => ["*/10 * * * *", "Every 10 minutes"],
+			"every hour" => ["0 * * * *", "Every hour"],
+			"fixed minute each hour" => [
+				"15 * * * *",
+				"At 15 minutes past every hour",
+			],
+			"midnight" => ["0 0 * * *", "At 12:00 AM"],
+			"noon" => ["0 12 * * *", "At 12:00 PM"],
+			"morning leading zeroes" => ["05 01 * * *", "At 01:05 AM"],
+			"afternoon" => ["5 13 * * *", "At 01:05 PM"],
+			"late evening" => ["59 23 * * *", "At 11:59 PM"],
+			"complex minute fallback" => [
+				"5,35 9 * * *",
+				"At minute 5,35 of hour 9",
+			],
+			"complex hour fallback" => [
+				"0 9-17 * * *",
+				"At minute 0 of hour 9-17",
+			],
+		];
+	}
+
+	/** @dataProvider secondScheduleData */
+	public function testSecondSchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function secondScheduleData():array {
+		return [
+			"every ten seconds" => ["*/10s * * * *", "Every 10 seconds"],
+			"fixed second" => [
+				"5s * * * *",
+				"At 5 seconds past every minute",
+			],
+			"complex second fallback" => [
+				"5,10s * * * *",
+				"At second 5,10 of every minute",
+			],
+		];
+	}
+
+	/** @dataProvider nicknameScheduleData */
+	public function testNicknameSchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function nicknameScheduleData():array {
+		return [
+			"hourly" => ["@hourly", "Every hour"],
+			"daily" => ["@daily", "At 12:00 AM"],
+			"weekly" => ["@weekly", "At 12:00 AM, only on Sunday"],
+			"monthly" => [
+				"@monthly",
+				"At 12:00 AM, on day 1 of the month",
+			],
+			"yearly" => ["@yearly", "At 12:00 AM, on 1st January"],
+			"annually" => ["@annually", "At 12:00 AM, on 1st January"],
+			"uppercase nickname" => ["@DAILY", "At 12:00 AM"],
+		];
+	}
+
+	/** @dataProvider weekdayScheduleData */
+	public function testWeekdaySchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function weekdayScheduleData():array {
+		return [
+			"weekday name" => [
+				"0 0 * * FRI",
+				"At 12:00 AM, only on Friday",
+			],
+			"weekday number" => [
+				"0 0 * * 5",
+				"At 12:00 AM, only on Friday",
+			],
+			"sunday zero" => [
+				"0 0 * * 0",
+				"At 12:00 AM, only on Sunday",
+			],
+			"sunday seven" => [
+				"0 0 * * 7",
+				"At 12:00 AM, only on Sunday",
+			],
+			"weekday range" => [
+				"0 22 * * MON-FRI",
+				"At 10:00 PM, only on Monday through Friday",
+			],
+			"weekday list" => [
+				"0 9 * * MON,WED,FRI",
+				"At 09:00 AM, only on Monday, Wednesday and Friday",
+			],
+		];
+	}
+
+	/** @dataProvider dayOfMonthScheduleData */
+	public function testDayOfMonthSchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function dayOfMonthScheduleData():array {
+		return [
+			"first day monthly" => [
+				"0 0 1 * *",
+				"At 12:00 AM, on day 1 of the month",
+			],
+			"thirteenth day or friday" => [
+				"0 12 13 * FRI",
+				"At 12:00 PM, on day 13 of the month or on Friday",
+			],
+			"complex day fallback" => [
+				"0 0 1,15 * *",
+				"At 12:00 AM, on day 1,15 of the month",
+			],
+		];
+	}
+
+	/** @dataProvider monthScheduleData */
+	public function testMonthSchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function monthScheduleData():array {
+		return [
+			"month name" => [
+				"0 0 * JAN *",
+				"At 12:00 AM, only in January",
+			],
+			"month number" => [
+				"0 0 * 1 *",
+				"At 12:00 AM, only in January",
+			],
+			"month list" => [
+				"0 0 * JAN,MAR *",
+				"At 12:00 AM, only in January and March",
+			],
+			"month range" => [
+				"0 0 * JAN-MAR *",
+				"At 12:00 AM, only in January through March",
+			],
+			"first of january" => [
+				"0 0 1 JAN *",
+				"At 12:00 AM, on 1st January",
+			],
+			"second of february" => [
+				"0 0 2 FEB *",
+				"At 12:00 AM, on 2nd February",
+			],
+			"third of march" => [
+				"0 0 3 MAR *",
+				"At 12:00 AM, on 3rd March",
+			],
+			"eleventh of april" => [
+				"0 0 11 APR *",
+				"At 12:00 AM, on 11th April",
+			],
+			"twenty second of may" => [
+				"0 0 22 MAY *",
+				"At 12:00 AM, on 22nd May",
+			],
+		];
+	}
+
+	/** @dataProvider nthWeekdayScheduleData */
+	public function testNthWeekdaySchedules(
+		string $expression,
+		string $expected
+	):void {
+		$explainer = new CronExplainer();
+
+		self::assertSame($expected, $explainer->explain($expression));
+	}
+
+	public static function nthWeekdayScheduleData():array {
+		return [
+			"first sunday" => [
+				"05 01 * * SUN#1",
+				"At 01:05 AM, on the first Sunday of the month",
+			],
+			"second sunday in may" => [
+				"05 01 * MAY SUN#2",
+				"At 01:05 AM, on the second Sunday of the month in May",
+			],
+			"third numeric weekday" => [
+				"0 0 * * 3#3",
+				"At 12:00 AM, on the third Wednesday of the month",
+			],
+			"fifth friday" => [
+				"0 0 * * FRI#5",
+				"At 12:00 AM, on the fifth Friday of the month",
+			],
+			"sunday seven" => [
+				"05 01 * * 7#1",
+				"At 01:05 AM, on the first Sunday of the month",
+			],
+			"mixed nth and standard weekday syntax" => [
+				"0 0 * * SUN#1,FRI",
+				"At 12:00 AM, on the first Sunday of the month and Friday",
+			],
+		];
+	}
+
+	/** @dataProvider invalidExpressionData */
+	public function testInvalidExpressionsThrow(string $expression):void {
+		$explainer = new CronExplainer();
+
+		self::expectException(InvalidArgumentException::class);
+
+		$explainer->explain($expression);
+	}
+
+	public static function invalidExpressionData():array {
+		return [
+			"empty" => [""],
+			"unknown nickname" => ["@sometimes"],
+			"too few fields" => ["0 0 * *"],
+			"too many fields" => ["0 0 * * * *"],
+			"invalid minute" => ["ABC 0 * * *"],
+			"minute out of range" => ["60 0 * * *"],
+			"hour out of range" => ["0 24 * * *"],
+			"day of month out of range" => ["0 0 32 * *"],
+			"month out of range" => ["0 0 * 13 *"],
+			"weekday out of range" => ["0 0 * * 8"],
+			"nth weekday zero" => ["0 0 * * SUN#0"],
+			"nth weekday too high" => ["0 0 * * SUN#6"],
+			"nth weekday range" => ["0 0 * * MON-FRI#1"],
+			"invalid seconds" => ["*/0s * * * *"],
+		];
+	}
+}
diff --git a/test/phpunit/CronExpressionTest.php b/test/phpunit/CronExpressionTest.php
index 7b48783..eac1ba7 100644
--- a/test/phpunit/CronExpressionTest.php
+++ b/test/phpunit/CronExpressionTest.php
@@ -64,6 +64,41 @@ public function testNicknameExpansion():void {
 		self::assertSame("2026-03-12 00:00:00", $nextRunDate->format("Y-m-d H:i:s"));
 	}
 
+	public function testNicknameExpansionIsCaseInsensitive():void {
+		$expression = new CronExpression("@DAILY");
+		$nextRunDate = $expression->getNextRunDate(new DateTime("2026-03-11 12:34:00"));
+		self::assertSame("2026-03-12 00:00:00", $nextRunDate->format("Y-m-d H:i:s"));
+	}
+
+	public function testNthWeekdayOfMonth():void {
+		$expression = new CronExpression("05 01 * * SUN#1");
+
+		self::assertTrue($expression->isDue(new DateTime("2026-03-01 01:05:00")));
+		self::assertFalse($expression->isDue(new DateTime("2026-03-08 01:05:00")));
+		self::assertFalse($expression->isDue(new DateTime("2026-03-01 01:06:00")));
+	}
+
+	public function testNthWeekdayOfMonthSupportsSundaySeven():void {
+		$expression = new CronExpression("05 01 * * 7#1");
+
+		self::assertTrue($expression->isDue(new DateTime("2026-03-01 01:05:00")));
+		self::assertFalse($expression->isDue(new DateTime("2026-03-08 01:05:00")));
+	}
+
+	public function testNthWeekdayCanBeCombinedWithStandardWeekdaySyntax():void {
+		$expression = new CronExpression("0 0 * * SUN#1,FRI");
+
+		self::assertTrue($expression->isDue(new DateTime("2026-03-01 00:00:00")));
+		self::assertTrue($expression->isDue(new DateTime("2026-03-13 00:00:00")));
+		self::assertFalse($expression->isDue(new DateTime("2026-03-12 00:00:00")));
+	}
+
+	public function testGetNextRunDateForNthWeekdaySchedule():void {
+		$expression = new CronExpression("05 01 * * SUN#1");
+		$nextRunDate = $expression->getNextRunDate(new DateTime("2026-03-01 01:05:00"));
+		self::assertSame("2026-04-05 01:05:00", $nextRunDate->format("Y-m-d H:i:s"));
+	}
+
 	public function testGetNextRunDateUsesSecondPrecisionForSecondStepSyntax():void {
 		$expression = new CronExpression("*/10s * * * *");
 		$nextRunDate = $expression->getNextRunDate(new DateTime("2026-03-11 12:34:25"));