Until I was about fifteen all schools where I grew up (just outside London)started late on All Saint's day to allow people to go to church. After that it changed so that you could ask permission to go but if you were not attending church you had to go to school. Same on Ash Wednesday. I see no surprise that so many religions have celebrations at similar times. Early civilisations wondered at the power of nature and so major festivals often fall at times when day length or seasons change. Later religions, particularly Christianity, chose to impose there own festivals at these times to try to incorporate pagan festivals into the church calendar.
I just enjoy the excuse to have fun!