  S                 English ordinal suffix for day of the     ``'st'``, ``'nd'``, ``'rd'`` or ``'th'``
                    month, 2 characters.
  t                 Number of days in the given month.        ``28`` to ``31``
  T                 Time zone of this machine.                ``'EST'``, ``'MDT'``
  u                 Microseconds.                             ``0`` to ``999999``
  U                 Seconds since the Unix Epoch
                    (January 1 1970 00:00:00 UTC).
  w                 Day of the week, digits without           ``'0'`` (Sunday) to ``'6'`` (Saturday)
                    leading zeros.
  W                 ISO-8601 week number of year, with        ``1``, ``53``
 
</s> remove         "Microseconds"
        return self.data.microsecond
 </s> add         "Microseconds; i.e. '000000' to '999999'"
        return '%06d' %self.data.microsecond
u                 Microseconds.                             ``000000`` to ``999999``
  S                 English ordinal suffix for day of the     ``'st'``, ``'nd'``, ``'rd'`` or ``'th'``
                    month, 2 characters.
  t                 Number of days in the given month.        ``28`` to ``31``
  T                 Time zone of this machine.                ``'EST'``, ``'MDT'``
u                 Microseconds.                             ``000000`` to ``999999``
  U                 Seconds since the Unix Epoch
                    (January 1 1970 00:00:00 UTC).
  w                 Day of the week, digits without           ``'0'`` (Sunday) to ``'6'`` (Saturday)
                    leading zeros.
  W                 ISO-8601 week number of year, with        ``1``, ``53``
keep keep keep keep replace keep keep keep keep keep
 Fixed #18951 -- Formatting of microseconds.

Thanks olofom at gmail com for the report. 
docs/ref/templates/builtins.txt