I just tested time based service on IAP (running 6.5.4.8) and it worked as expected. The SSID is down once the end time is reached.
Followign is configuration and test result.
Do validate the configuration and see if you have missed anything. Work with TAC, if your configuration is good and issue exists.
18:64:72:c8:20:a0# show time-range | include test
test Periodic thursday 23:00 thursday 23:10 No
18:64:72:c8:20:a0# show time-profile | include test
test Time_range_test Enable
>SSID not ON before the clock.
18:64:72:c8:20:a0# show clock
Current Time :2018-08-23 22:58:10
18:64:72:c8:20:a0# show ap bss-table | include Time_range_test
>SSID is ON during the range.
18:64:72:c8:20:a0# show clock
Current Time :2018-08-23 23:00:33
18:64:72:c8:20:a0# show ap bss-table | include Time_range_test
18:64:72:02:0a:03 Time_range_test ?/? 10.x.x.x g-HT ap 1/18.5/18.5 0 18:64:72:c8:20:a0 0 22s
18:64:72:02:0a:13 Time_range_test ?/? 10.x.x.x a-VHT ap 116E/27.0/28.5 0 18:64:72:c8:20:a0 0 22s
>SSID is OFF after the end time.
18:64:72:c8:20:a0# show clock
Current Time :2018-08-23 23:10:28
18:64:72:c8:20:a0# show ap bss-table | include Time_range_test
18:64:72:c8:20:a0#