Cron every day at midnight: 0 0 * * *

Midnight is hour 0, not hour 24. The hour field is defined as 0 to 23, so 0 24 * * * is rejected as out of range rather than silently treated as the end of the day. Once that is clear the expression is the simplest daily schedule there is: minute 0, hour 0, every date.

It is also the single most crowded moment on any server. Log rotation, backup scripts, certificate checks, report generation and every job written by somebody who wanted it to run daily all land in the same second. If a nightly job is mysteriously slow, the first thing to check is how many other things start at exactly the same time.

Spreading that load is easy and almost always worth doing. Nothing about a nightly job usually requires midnight specifically, so 0 1 * * * or 23 0 * * * are equally valid and dramatically less contended. Reserve midnight for the job that genuinely has to be first, such as rolling the date partition everything else writes into.

There is a timezone subtlety unique to midnight. A handful of zones make their daylight saving transition at 00:00, which means the 00:00 wall clock time either does not occur or occurs twice on those days. Implementations differ in how they compensate, so if the job must run exactly once a day, run the crontab in UTC or make the work idempotent.