The famous Sri Ganga Aarti in Haridwar has a change of timing. This change is based on sunrise and Sunset. This change is done every year. Shri Ganga Sabha changes the timings according to the season. In the winter arti starts at 7 in the morning and evening prayers at 5.40 pm. During the summer season arti wil start at quater past five o'clock in the morning and evening prayers at 7.40 pm. The new timings will come into effect from june.

Thanks a lot for the information, it was really useful for scheduling my grandmother's visit.