You could have an additional field called [TIME_ZONE]. It would have to be
entered by the user.
What I don't know is what time zone you are in, whether you are looking at
only US time zones, or global time zones, etc.  If you are using only US time
zones, I would store all times in EST(Not Daylight Savings, we'll get to
that) then for the values in [TIME_ZONE] I would use:
EST = 0
CST = 1
MST = 2
PST = 3

Then, to display the user's time in his local time:
=DateAdd("h",-rst![TIME_ZONE],rst![THE_TIME])
Now, as to Daylight Savings,  When it is in effect, you would need to add
this:
=DateAdd("h",-rst![TIME_ZONE]+1,rst![THE_TIME])
Here it gets sticky. There is probably a way to query the system time and
determine if it is on DST or not, but I don't know how.  The other problem
is, that not all places in the US go on DST, Arizona, for example, ignores it.
(That is why it is a desert, the extra hour of sunlight burns up all the
vegetation)
And, there might be a 3rd party product that will know what the correct time
is for a location.