Getting correct (synced time) from `AT+CCLK?`

We are using Calliope (GC02S1-EU2) on our IoT gateway. The gateway needs to run CCLK for several reasons and we found some time sync issues. Later, we discovered that the fetched time was wrong.

D (28456) AgNode: TX: AT+CEREG?
D (28456) AgNode: RX: +CEREG: 1,5
D (28456) AgNode: RX: OK
D (28456) AgNode: TX: AT+CCLK?
D (28466) AgNode: RX: +CCLK: "70/01/01,00:00:16+00"
D (28466) AgNode: RX: OK

I (28476) app: Unix time received: 3155760016

Questions:

  • Is "70/01/01,00:00:16+00" a default value of some sorts?
  • Is there some ideal time we should wait to get the correct value or is there some command to check if the time has actually synced.
  • What’s the recommended application domain logic to avoid this situation?

For reference, 70/100 times, the time is indeed correct as follows

D (26463) AgNode: TX: AT+CEREG?
D (26463) AgNode: RX: +CEREG: 1,5
D (26463) AgNode: RX: OK
D (26463) AgNode: TX: AT+CCLK?
D (26473) AgNode: RX: +CCLK: "25/12/19,16:33:18+04"
D (26473) AgNode: RX: OK

I (26483) app: Unix time received: 1766158398