You're lucky, because amigadiary is approaching end of life :
4. (Not a bug) I never expected people to want to insert entries
in the past, so I made the lookup date routine add 2000 to the
year if it was less than 90. It would seem, however, that
if you were keeping records or something then you might want
entries in previous years. Now, only years less than 30 are
21st century. Any others go to 20th century, so for example if
you entered 69 it would become 1969, not 2069. This means the
diary can be used up until 2030. If anyone is still using it
after that don't expect help from me!