In the presentation, I will:

1. review the "unit of time" which was earlier on based on the movements of astronomical objects

2. review the history of time keeping devices (in terms of origin, how they work etc. ...)

3. and finally I will introduce the atomic clock and how time keeping is done today.

The presentation will be based on the paper:

• A Comprehensive overview of atomic clocks and their applications, Thejesh N Bandi, BEMS Reports 9, 1 (2023) https://doi.org/10.5530/bems.9.1.1

and additional sources from Wikipedia (or here and there).