Minute is defined in RFC 3339 as A period of time of 60 seconds.

However, see also for how Leap seconds seconds are denoted within minutes.

Minute is equal to  1⁄60 (the first sexagesimal fraction) of an hour, or 60 seconds. In the UTC time standard, a minute on rare occasions has 61 seconds, a consequence of leap seconds (there is a provision to insert a negative leap second, which would result in a 59-second minute, but this has never happened in more than 40 years under this system). [1]

More Information#

There might be more information for this subject on one of the following:
  • [#1] - Minute - based on information obtained 2017-10-14-