For any timestamp in REST API, YouTrack uses Java timestamp format: The number of milliseconds since January 1, 1970, 00:00:00 GMT. This format is similar to Unix time, but is defined in milliseconds as opposed to seconds.
The most frequently met timestamps:
- Issue timestamps: created, updated, resolved, updatedAfter, and any issue field of date type.
- Comment timestamps: created and updated times
- Attachment timestamp: created time