The standard version of dosemu emulates the DOS clock by counting interrupts but this means that the DOS session will slowly depart from the host's time.
This patch adds a configuration option to dosemu.conf for choosing Linux time. Assuming Linux time is synchronised to NTP then this will keep the DOS session synchronised too.
Alternatively view the patch directly as patch-1.2.0-mods7-v2.
NOTE: There is a small bug in the patch which will affect the emulator if it rolls over a new year. Contact me for a fix.
Documentation is available from Dr.Crawfords dosemu web site.