DMake uses the time-stamp of the files to determine whether a recompilation is neccessary. If you do not have a clock, or it doesn't always function properly (mine sometimes sets itself back to Jan-78) in an unlucky case it could happen that a freshly edited dependent file has an older time stamp than its target file, causing DMake not to resolve the dependency (and your bug-fix or added feature not showing up).
e.g. having the following dependancy,
main.o : main.csay the target main.o already exists from a previous session, in this session your timer misbehaves (setting itself back to the 70's) and you edited main.c, the new file won't be recompiled.
dcc main.c -o main.o
The solution is either