hi guyz i need ur help!!

how could i convert the time format for example i have a time 4:56 pm and i want to convert it in 16:56 so that the if i query it from the database it displays the result.?

on more thing how would i iterate in this format

00
01
02
03
04
05
06
07
08
09
if i use this:
for (i=0;i>10;i++)

the result would be
123456789

how would i put 0's in my iteration so that it would be 2 numbers?