Colin Law wrote:
> I would suggest changing the fields to DateTime. Then you will be
> able to do direct comparisons.
>From someone who has been burned by this in the past, I have a slightly
different suggestion.
If you actually do need to store a time that is independent of a date, I
would recommend storing time as an offset. Something like seconds from
midnight. Store this value as an integer in the database.
Using such a technique eliminates dependency on the geo-political rules
governing the representation of dates and times.
For convenience you could add an instance method to give you the time of
day as a string.
# Assume the "time_offset" column contains 25000 (seconds from midnight)
def presentable_time
t = Date.today.to_time + self.time_offset.seconds
t.strftime("%I:%M %p")
end
puts my_object.presentable_time
=> "06:56 AM"
With this technique your "difference" or "duration" calculations become
trivial:
time_diff_seconds = obj_1.time_offset - obj_2.time_offset
It's not that common that one needs to store time independently of date.
However, one case that comes to mind would be if you were calculating
statistics based on time of day. Maybe you would want a graph showing
activity based on the time of day. If you're doing something like that
then having the time of day stored separately from the date would
simplify the queries.
select * from orders where time_offset between 46800 and 54000;
would select all orders placed between 1:00 PM and 3:00 PM
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