fix(capture): document UTC timestamp normalization - #45
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dustinbyrne merged 1 commit intoAug 20, 2026
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Nine SDKs independently fixed the same bug this week: caller-supplied timestamps were serialized in their original timezone/offset instead of being normalized to UTC, and fractional seconds were sometimes truncated. The spec only said "ISO 8601 with timezone," which doesn't capture that the timezone is always UTC. Generated-By: PostHog Desktop Task-Id: 3ddf61c1-e6f7-46b2-b8d4-06a71a62848f
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dustinbyrne
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August 20, 2026 20:31
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Summary
capturespec's "Attach envelope fields" step:timestampis normalized to its equivalent UTC instant before serialization (not left in the caller's original timezone/offset), and sub-second precision is preserved when present on the input.Why
Nine SDKs merged the same fix within a day of each other (2026-08-13/14): caller-supplied
timestampoverrides (and posthog-php's parsed default) were serialized with their original UTC offset intact instead of being converted to UTC, and fractional seconds were sometimes truncated to whole seconds.Source PRs:
The spec previously said timestamps are serialized "in ISO 8601 with timezone" — true but incomplete, since it didn't say the timezone is always UTC. A new SDK implemented from this spec alone would have shipped the exact bug these nine PRs just fixed.
Prose-only change (no requirement/scenario text touched — none assert a specific timezone), archived directly per this repo's convention for prose fixes (see
2026-08-13-fix-node-shutdown-timeout-resolvesfor precedent).Uncertain / follow-up
tasks.mdas a follow-up, not asserted either way.openspec validate --specs --strictcould not be run locally (CLI unavailable in this sandbox); please confirm CI passes.Created with PostHog Desktop