Date Field Serialization#

Strapi distinguishes between date, datetime, and timestamp field types. The date type stores only a calendar date and requires strict YYYY-MM-DD format on the wire — no time component, no timezone suffix. The datetime and timestamp types accept full ISO 8601 strings.

Backend: Parsing and Validation#

The canonical parsing logic lives in packages/core/database/src/fields/shared/parsers.ts.

• parseDate 1 — The authoritative handler for date fields. It:

  1. Validates the input against DATE_REGEX (/^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$/) 2.

  2. If the input contains a valid date prefix but also carries extra characters (e.g., a full ISO timestamp like 2024-12-07T00:00:00.000Z), it extracts the date portion via PARTIAL_DATE_REGEX and emits a process.emitWarning 3:

     [deprecated] Using a date format other than YYYY-MM-DD will be removed in future versions. Date received: <value>. Date stored: <extracted>.

  3. If no extractable date prefix exists at all, it throws InvalidDateError 4.

  4. Returns only the YYYY-MM-DD portion — the time component is always discarded 5.

  ⚠️ A TODO comment at line 45 marks this graceful fallback for removal — it will be replaced by a hard InvalidDateError in a future major version 6. Any integration that sends full ISO timestamps to a date field will break when that change lands.

• parseDateTimeOrTimestamp 7 — Used for datetime/timestamp fields; accepts full ISO strings and Unix millisecond timestamps via date-fns.parseISO and date-fns.parse.

Admin Frontend: Date Picker Component#

The Admin UI date picker is in packages/core/admin/admin/src/components/FormInputs/Date.tsx.

Key behavior 8:

• On each date selection, the picker converts the local Date object to UTC midnight via toUTCMidnight 9, then serializes with utcDate.toISOString().split('T')[0] — stripping the time component before dispatching field.onChange.
• On blur with an invalid partial input, the field reverts to the last known valid value using the same split('T')[0] pattern 10.
• maxDate is capped at 2099-12-31 11.

Why this matters: Before PR #25372, the picker was sending utcDate.toISOString() (e.g., 2024-12-07T00:00:00.000Z). This triggered the backend deprecation warning on every save, and would have caused hard failures once the TODO-marked error is enabled 12.

Format Summary#

Common Failure Modes#

• Sending a full ISO string to a date field (e.g., from a custom integration or older Admin version): triggers the [deprecated] process.emitWarning today; will throw InvalidDateError in future versions.
• Timezone drift: toUTCMidnight anchors dates to UTC midnight so local-time offsets don't shift the stored date by one day. Any code outside the Admin UI that constructs date strings should apply the same UTC normalization before slicing off the time portion.
• Invalid or unparseable values (no date prefix at all): immediately throw InvalidDateError — no fallback or warning 4.

Key Source Files#