Use AT+CIPGSMLOC command. It works well in SIMCOM modules.
This command needs the GPRS service attached before you use it. So first attach the GPRS service using appropriate command sequence then use this command to get date and time from GSM network.
For attaching GPRS service:
CMD:AT+SAPBR=2,1 /* to confirm that GPRS is attached. will show IP if attached */
Then use GSM Location command:
This command needs considerable time (few seconds) to get the information from network so give the command execution function proper timeout.
This command also returns the BTS location which the module is connected to. So you can get a roughly accurate location of the GSM module as well.
Refer to this manual for more information: (works the same way for SIM800)
SIM900_GSM Location AT Command Manual_V1.00
Also note that the AT+CLBS command is not the same as this command. It may not work in some regions. (I haven't been able to use it!). But the AT+CIPGSMLOC always works.