[ns] how to obtain current virtual time in ns2.29

[BENMESSAOUD ASMA]

Hi every body , 
 
i want to calculate a current virtual time in ns-2.29 . i already used "now" 
but the values which are returned are different about the values of time which 
we find in file trace for example . and me , search a function which gives a 
time like a trace file .
 
Please reply , it's veeeeeeery important for me .
thanks a lot in advance .
Asma.