Web alarm clock for 9:37 p.m.
As you watch the clock for the moment to close your neighbourhood sari-sari store before evening prayer, set the alarm for 9:37 pm and keep serving the last customers without checking the time after every sale. The signal leaves 23 minutes before 10:00 pm, enough for you to secure the counter, bring small displays inside, and prepare to step away.
Before relying on the alarm to mark the shop-closing moment, check whether your phone is on silent or its alert volume has been turned down. A browser alarm may appear on screen without making the sound you expect under those settings. It also cannot signal the shop closure if the page is no longer open or the phone has gone to sleep, so keep the page active and the phone awake until 9:37 pm.
Because the evening prayer schedule can affect everyone sharing the house, place the phone near you rather than beside someone who is resting, studying, or settling a child. Choose a clear but moderate volume, and tell anyone helping at the store that 9:37 pm is the agreed cue. You can then close shutters and put away stock quietly without turning one alarm into a disturbance for the household.