Hence I performed the following simple tests to check out year 2000 readyness. As you can see, mtools handles dates beyond 2000 all right. However, as this later problem is tied to the 32 bit storage size of current Unix dates, the problem will likely have disappeared on its own by then. Here is the specific information that I need. These tests were performed using mtools-3.8, released on August 7th, 1997.
All later versions are ok as well.
Indeed, none of the recent changes involved this issue. The C library used was libc.so.5.4.38. Very old libc's could conceivably have problems here. Libc's on Unices other than Linux could have problems too. When 3.9.4 will come out, 3.9.3 will be removed.