My husband's office has phones but no manuals

I tried looking through the manuals and finally came upon a reference that said the System Administrator Guide was where to look because only that special system was able to do it.

It has the instructions to set the time on page 12

http://www.deltaintellicom.com/wp-content/uploads/2014/07/System-Admin-Guide-Toshiba-DK-Systems.pdf

You'll need an HHEU Headset Interface which installs inside the set via a ribbon cable.

Older DK systems are very difficult unless you work with them frequently. Newer CiX systems use the eManager interface.

# 652, key HH:MM:SS, #

here is a link to the manual for this phone hope it helps. Strata CTX DKT/IPT manual

my office manager quite & he did tell us the code to the phone directory, so how can i get that code???

You can log into mail box 999 with sec code 999997 or 997 and press 8 for admin features. here is a good site to mind your manual and guides
http://guides.idacomusa.com/

Judging on your phone model I think you have a CTX system. dial # 651 for date in YYMMDD and #652 for time in HHMMSS and press # when done. Your manual and good guides are located here.
http://guides.idacomusa.com/

This feature requires you to go into system programming to change the hold reminder time. Different Systems have different codes in programming. If you have the system programming manual specific to your system, it should be relatively easy to change that. Or, you could ask your system administrator to do it for you.

I couldn't find the manual for your specific phone, but you can try manual these similar phones.

http://www.tel-programmer.com/Time%20setting/toshiba_time.htm