What is the difference between a retentive timer and a non$-$retentive timer in a PLC$?$

Non$-$retentive timers are generally faster than retentive timers.

Retentive timers require a battery backup to maintain their state during power outages, while non$-$retentive timers do not.

Retentive timers are used for counting events, while non$-$retentive timers are for timing delays.

A retentive timer remembers its elapsed time even during program execution pauses, while a non$-$retentive timer resets to zero.