To FootWith a count of seconds, days, years, etc., from a given Epoch, there will be some particular moments when the count reaches a numerically significant value. If these moments are not foreseen, unexpected errors in calculation may occur; many are included in Critical Dates.
For example, UNIX uses a GMT seconds count from Gregorian AD 1970-01-01 00:00:00 GMT; at 2038-01-19 03:14:08 GMT, 231 seconds will be reached, and a signed DWORD count (as generally used for time_t) will overflow, going from +2147483647 to -2147483648.
Given a set of Epoch dates and offsets from them, this page will list, in order, the results of all straight combinations. Offsets may be seconds from a particular moment, or days from a particular date, or both. A few initial entries are provided.
Depending on details, the date or time given may be the first/last good/bad one.
There is more on Epochs and Intervals in Zeroes of Date/Time Scales; see also in Date Miscellany I.
The "Enter" TextAreas are editable (the order of lines is immaterial); after editing, press the appropriate button.
Epoch entries must be date/times, optionally with comment after semi-colon. Count entries have three fields, two numeric and one word.