Dates & Times

Date and time formats are specified as ISO8601 compatible strings, both for time points as well as for intervals and durations.

An optionally required granularity may be specified as part of the respective attributes' documentations.


  • external information can be found at W3C: [ISO8601](

Units of time

Time points

The specification of a time point is given through the concatenation of




Durations are the most common form of time intervals. They do not refer to (e.g. start or end) time points. They are indicated with a leading “P”, followed by unit delimited quantifiers. A leading “T” is required before the start of the time components. Durations do not have to be normalized; “PT50H” is equally valid as “P2T2H”. A frequent use of durations in biomedical data resources are age values, e.g. “age at diagnosis”; but also “progression free survival”, “followup” or “time to recurrence” (these are descriptive labels, which do not necessarily represent GA4GH schema use).


Time intervals

Time intervals consist of a combination of two time designators. These can be either two time points for start and end, or one time point and a leading (time point indicates end) or trailing (time point indicates start) duration. The time elements are separated by a forward slash “/”.

While such anchored time intervals represent an option to capture different time features in a single value and to avoid disconnected references, in the context of the data schema, anchored intervals will presumably be used less frequently, with a qualitative anchor (“date of diagnosis”, “time of sampling”) representing the point of reference.


@mbaudis 2018-12-21
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