works fine on CLI, issue only on UI. will be fixed in coming releases. thanks for reporting this Colin.
ac:a3:1e:c6:d6:30 (config) # time-range testhelp123 periodic sunday 21:00 to monday 06:00
ac:a3:1e:c6:d6:30 (config) # end
ac:a3:1e:c6:d6:30# commit apply
committing configuration...
configuration committed.
Show command output
ac:a3:1e:c6:d6:30#
ac:a3:1e:c6:d6:30# sh time-range
Current Time :2016-04-26 11:05:03
Time Range Summary
------------------
Profile Name Type Start Day Start Time End Day End Time Valid
------------ ---- --------- ---------- ------- -------- -----
help_test Periodic monday 01:00 sunday 02:00 Yes
testing Periodic monday 10:20 tuesday 10:30 No
testhelp123 Periodic sunday 21:00 monday 06:00 No