Support some type of jitter or randomness to avoid many jobs starting at the same time when it does not really matter.

[norman-abramovitz]

Jenkins uses the H symbol to represent the randomness of startup times.

https://www.jenkins.io/doc/book/pipeline/syntax/#cron-syntax

The H symbol can be used with a range. For example, H H(0-7) * * * means some time 
between 12:00 AM (midnight) to 7:59 AM. You can also use step intervals with H, with or 
without ranges.

The H symbol can be thought of as a random value over a range, but it actually is a hash 
of the job name, not a random function, so that the value remains stable for any given project.

Beware that for the day of month field, short cycles such as */3 or H/3 will not work consistently 
near the end of most months, due to variable month lengths. For example, */3 will run on 
the 1st, 4th, …31st days of a long month, then again the next day of the next month. Hashes are 
always chosen in the 1-28 range, so H/3 will produce a gap between runs of between 3 and 6 days
at the end of a month. Longer cycles will also have inconsistent lengths, but the effect may 
be relatively less noticeable.