You still didn't answer my question regarding "it works for me".

No need to repeat the information that your 8051 only have two timers.

That is not a problem since a single 10ms timer can both generate 10ms+ delays for the EEPROM and count seconds/minutes/hours.

Note that a freerunning 10ms timer requires you to wait for two interrupts (getting a delay in the [10..20) range) since you may have started the wait just before the next interrupt. More exact time can be had by not looking for the interrupts but instead reading out the timer value but that is probably not needed in your case.

And in some situations - depending on what baudrate you are using - it's possible to count the number of times the baudrate timer gets reloaded using a busy-loop.