Adding an AM/PM indicator is quite easy.

Simpler power supply without battery back-up. If you do not need battery back-up capability, the power supply section can be simplified.

Modification of 7-segment display's font is not difficult. This is an idea related to the font for the numerical characters 6, 7 and 9, hence U8 and U10 in the schematic SD03020 are considered as targets of this modification.