The libV77 library is the VMS library, which contains two special VMS routines, idate and time.
To use either of these routines, include the -lV77 option.
For idate and time, there is a conflict between the VMS version and the version that traditionally is available in UNIX environments. If you use the -lV77 option, you get the VMS compatible versions of the idate and time routines.
See the Fortran Library Reference Manual and the FORTRAN 77 Language Reference Manual for details on these routines.