compound if alternatives

[Robert Brenstein]

I need to repeatedly check within which of predefined time periods 
the current moment is. Since this affects overall performance (but is 
necessary), I am trying to see whether there is an alternative to a 
compound if to speed this up.

t1, t2, t3, ... , t7 -- time interval boundaries in seconds
c - current time in seconds

if c < t1 then
   do1
else if c >= t1 and c < t2 then
   do2
else if c >= t2 and c < t3 then
   do3
...
else if c >= t7 then
   do8
end if

Anyone any ideas? I seem to have a "writer's block" :(

This is for a cgi handler on a web server that controls user actions 
over a time span. For each user request I need to determine which 
time period I am in and then take appropriate action (or tell user 
that his request is not allowed at this time).

Robert