Trigger runs based on a cron like schedule. You can use the regular Jenkins syntax but also an extended syntax. See the tables below for reference.
The extended syntax has limited support for the H character. It can only be used standalone and not in combination with ranges or intervals.

Timezone
To specify a different timezone use

TZ=Europe/London

The timezone can appear anywhere in the list, also multiple times and applies to all following lines until a new timezone definition is found.
To reset the TZ information to the controller timezone use

TZ=

Parameters
To define parameters that should be passed to a schedule start the next line with a % followed by `name=value`. If you want to have a parameter take a multiline value prefix the next line with %%. For better readability you might want to indent the parameter definitions. Each line after the cron spec that starts with `%` is interpreted as parameter until a new cron spec or timezone definition is found.

0 12 L * * *
  %param1=foo;bar
  %param2=bar
  %%baz
  %param3=value // this is not a comment
  

Comments
Lines starting with `#` are comments. You can also add comments with `//` after a cron entry but not in parameters. `#` is not allowed to make the rest of the line a comment.
Extendend Cron Syntax

Field	Allowed Values	Allowed Special Characters	Comment
Minutes	0-59	, - * / H
Hours	0-23	, - * / H
Day-of-Month	1-31	, - * / ? L W H
Month	1-12 or JAN-DEC	, - * / H	case doesn't matter
Day-of-Week	0-7 SUN-SAT	, - * / ? L # H	0 or 7 is sunday, case doesn't matter

Special Characters

Char	Description
*	Matches all values of the field. E.g. * in the minute field means every minute.
?	Stands for 'no specific value' and is allowed for the Day-of-Month and Day-of-Week fields. It is used instead of the asterisk (*) for leaving either Day-of-Month or Day-of-Week blank.
-	Used to define ranges. E.g., 10-12 in the hour field means the hours of 10, 11, and 12.
,	Used to separate items in a list. E.g., MON,WED,FRI in the Day-of-Week field means the days Monday, Wednesday, and Friday.
/	Used to indicate increments. E.g. 0/20 in the minutes field means the seconds 0, 20 and 40. 1/4 in the Day-of-Month field means every 4 days starting on the first day of the month.
L	Short for "last" and can be used in the Day-of-Month and Day-of-Week fields. The L character has a different meaning in the two fields. In the Day-of-Month field, it means the last day of the month. In the Day-of-Week field, it means 6 or SAT. If used in the Day-of-Week field after a number, it means the last xxx day of the month. E.g., 6L in the Day-of-Week field means the last Saturday of the month.
W	W Stands for "weekday" and is only allowed for the Day-of-Month field. The W character is used to specify the weekday nearest to the given day. E.g., 10W in the Day-of-Month field means the nearest weekday to the 10th of the month. If the 10th is a Saturday, the job will run on Friday the 10th. W can be combined with L to LW and means last weekday of the month.
#	Can only be used in the Day-of-Week field. Used to specify constructs. E.g., 5#3 means the third Friday of the month.
H	Stands for a random value (based on the hash of the job name). Must be used standalone or in combination with a range e.g. H(0-4). In the Day-of-Month field values are chosen in the 1-28 range.