When to use DST rules

[seismo!celerity!dreamit!jjw]

All the versions of ctime that I am familiar with apply the daylight savings
time rules into the "distant" past and into the future.  This seems like
overkill.  Certainly, people want to see the time with DST applied for the
current year and it probably makes sense to apply the DST correction for the
previous year.  But is it really necessary to apply the DST rules when
listing times for data which is 2, 3, 5 or 10 years old?

Since the DST rules are subject to the whims of politicians and bureaucrats,
any rules beyond the next year are as likely to be wrong as right.

I ask this because it seems to me that a file containing several years of
Daylight Savings Rules can be expensive to search and a program to calculate
Daylight Savings time for multiple years is unnecessarily complex.  If we
only need to determine the rules for the last couple of years, and for the
next year, then time conversions will be faster and simpler.