Your process says nine o’clock. Nine o’clock where?
A scheduled task can run without errors and still arrive at the wrong time. This happens when a person thinks in local clock time while the system uses a different reference. Before starting a recurring process, define exactly what “at nine” means.
Write the rule before configuring it
“Every day at nine in Barcelona” is not the same as “every twenty-four hours”. The first follows a local clock; the second measures elapsed time. That difference matters when clocks change. MDN explains that a zoned date-time combines an instant, a time zone and a calendar, and that you cannot assume every day contains twenty-four hours.
For a daily report, write a readable rule: working days, local time, the Europe/Madrid time zone and the recipient. Add what happens on public holidays. If the system does not know the working calendar you need, do not assume that “Monday to Friday” already represents it.
Separate local time from the technical record
A named time zone such as Europe/Madrid is not equivalent to a fixed offset from UTC. Local rules can change. Keep the business rule with its time zone and record each execution as an unambiguous instant. This lets you explain when it was planned and when it actually happened without reinterpreting an isolated clock reading.
Test the cases that break the routine
In a test environment, check a clock change, a delayed execution and a service interruption. Decide what to do if a local time does not exist or occurs twice. Do not leave that decision to a setting nobody has read. Also define whether a recovered task should deliver late or skip that edition.
Avoid duplicating a late delivery
Assign an identifier to each planned delivery and check its status before repeating it. A “process started” notification does not confirm that the recipient received the result. Record preparation, attempt and confirmation separately. The final test is simple: someone on the team should be able to read the rule and predict the next delivery without working it out from memory.