“Surprisingly, chip is more complicated than I anticipated and digital part is less than ~50% of the die area.”
The F-91W was introduced in 1989, and the chip inside today’s version dates to 2006. More than half of the die is analog. Casio promises 30 seconds a month, and newer units run 7 to 10 years on one battery, up from 2. Your smartwatch needs a charger every night to tell the same time.