fix(mock): tests work when run in any time zone
fix(mock): correctly test subsecond precision
fix(date): works with 4 or more subsecond digits

Prior to this fix if the seconds had more than three digits
of precision the date would not be converted correctly.
For example {{2003-09-10T13:02:03.123456Z | date: yyyy-mm-dd ss}}
was treated as having 123456ms so 123 seconds would be added
to the time. With this fix 123456 is rounded to 0.123
seconds.