Real Time CLock

Just like to know if there are SEC, HOUR, … registers to access for the RTC or does one need to code the RTC using the millisecond timer that is available?

What is the maximum time in [ms’s] that the timer counts to? (u32 ?).

Thanks. 8)



The RTC can be accessed through the +CCLK command.

It can be configured with a string of the format:


The result string is the same also when reading the current value.

There are two different resolutions for using timers:
100 ms and 18,5 ms, both with a u32 TimerValue. I’m afraid you cannot get better resolution than 18,5 ms.

But if you want longer time than u32 * 100 ms, then you can of course implement software timers yourself…



be carefull the “100ms” timer is a 92.5ms timer (18.5 * 5). It may be critical if you use one of these timer several times (error will be multiplied).


Additional RTC service is avalaible in Open AT 3.10, you can get the time and convert it with native funtions, but if you want to set the RTC clock you still have to use the AT+CCLK command.


Hi all
How can RTC be set automaticly.


Hi Malek,

Some providers support NITZ, so you might be able to extract the time from WIND messages (I don’t know how…)


you could use GPRS to connect to a time-server through TCP or UDP.
See: RFC 868 (

Best Regards,

Thanks jan :slight_smile:
I will see with the two methods that u have told me.
But there is also an AT command in the module with the GPS part that set the GSM RTC with the GPS fixed time (AT+WGPSM=4)

But in the format of the response of this Command : there is no information about the indication of time zone. Have u some information about this.


Gps Rtc is GMT clock. Signal is directly provided by satellites, so they don’t know who (then which country) receive the signal.

Nitz info, provided by the GSM operator contain local info and time shifting.

GPS time is not directly GMT. The difference is ~13s at the time. Keep this in mind. On Q2501, we observed jumping the time from one to the other under some circumstances.
See at “GPS time and date”.

See also: … light=time