MediaWiki:Wikibase-listdatatypes-time-body/en

Literal data field for a point in time. Given as a date and time with some precision and boundaries. The time is saved internally in the specified calendar model.
 * time – explicit value for point in time, represented as a timestamp resembling ISO 8601, e.g. +2013-01-01T00:00:00Z. The year is always signed and padded to have between 4 and 16 digits.
 * timezone – explicit value as a signed integer. Timezone information as an offset from UTC in minutes.
 * before – explicit integer value for how many units after the given time it could be. The unit is given by the precision.
 * after – explicit integer value for how many units before the given time it could be. The unit is given by the precision.
 * precision – explicit value encoded in a shortint. The numbers have the following meaning: 0 - billion years, 1 - hundred million years, ..., 6 - millennium, 7 - century, 8 - decade, 9 - year, 10 - month, 11 - day, 12 - hour, 13 - minute, 14 - second.
 * calendarmodel – explicit value given as a URI. It identifies the calendar model of the timestamp.