The following tools can be found in the HYCOM source distribution.

The MT value is days since 1900-12-31 00:00:00, which is also the HYCOM model day or NRL wind day, so you can use hycom_ymdh_wind to find MT.

hycom_ymdh_wind

c
c     input:  yyyy mm dd hh (calendar/model year, month, day, and hour)
c     output: the HYCOM model day and yrflag(=3)
c
c --- wday   = wind day since 01/01/1901
c --- yrflag = days in year flag (3=actual)

Example:

ajax 100> echo 2012 02 01 00 | hycom_ymdh_wind
   40574.000  3