Environment variables can be set in each crontab.
PATH is especially useful to set there.
TZ can be set, but cron ignores it other than passing it on through to the commands it runs. Leading or trailing blanks can be preserved by quoting, single or double quotes are okay, just so they match. Case is not significant, but only the first three letters should be specified. Three letters only. Standard crons won't allow '1,3-5'.