Date and Time

• Based on ISO8601, an international standard for representing date and time. We chose the "extended format" with the hyphens because it is more human readable.

  • Compare 2016-01-01 to 20160101

• All date and time variables must be local time (UTC -8hrs Pacific Standard Time UTC -7hrs Pacific Daylight Savings Time) unless specified.

  • Use the data dictionary to specify any important information about time encoding

Date variables

For fiscal periods, prefix "fiscal_" to column name

• Fiscal year start date must be indicated in the data dictionary

  • e.g. The fiscal year starts on July 1 and ends on June 30 for the State of California

Date-time and time variables

• ISO 8601 uses 24 hour clock system in hh:mm:ss format sometimes referred to as military time (do not use AM or PM)

  • e.g. 13:00 is equivalent to 1:00 PM

Specify the timezone if it is not local time (UTC -8hrs Pacific Standard Time UTC -7hrs Pacific Daylight Savings Time):

Date and time extracts

In certain cases you may want to provide a single variable representing the number or name of an individual date component, a day, a month, etc. There's no requirement to provide these, but follow this guidance:

Durations

Durations can be automatically calculated if you provide a separate start and end period in your dataset. If you also want to provide a duration, please:

• Provide the milliseconds between the start and end period (include the duration unit in the data dictionary)

  • Milliseconds can be rolled up to other time intervals

• Use duration in your column name but prepend with a useful descriptor, e.g:

  • flight_duration

  • response_duration

  • dwell_time_duration

  • travel_duration

• Do not duplicate any of the duration column names per the guidance on columns