@abhishek2101, there is no Real Time Clock on the nRF52840 used by the mesh devices. Instead, it is a Real Time Counter which can be used by the DeviceOS to "simulate" a true RTC. However, this would not work in STANDBY sleep mode without waking the processor at regular intervals and would have considerable drift over time. I suggest you look at using an external independently powered RTC which could wake the processor from STOP or STANDBY sleep are needed. See here:
2 Likes