Why did secularists steal April 22 from Christians?

Earth Day is a day designed to inspire awareness and appreciation for the Earth's environment. It was founded by U.S. Senator Gaylord Nelson as an environmental teach-in held on April 22, 1970.[1] Earth Day is celebrated in spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Many communities celebrate Earth Week, an entire week of activities focused on environmental issues. The first Earth Week originated in Philadelphia in 1970 (starting April 16 and culminating on Earth Day, April 22.)[2] Earth Day Network, a group that wishes to become the coordinator of Earth Day globally, asserts that Earth Day is now observed on April 22 on virtually every country on Earth.[3] World Environment Day, celebrated on June 5 in a different nation every year, is the principal United Nations environmental observance.[4]

The Christians have stolen quite a few pagan dates themselves! When Christianity was in its early stages and the religious leaders were seeking to set dates for Christian holidays, they chose dates that coincided with pagan holidays. The idea was, if pagans are already celebrating on that day, it won't be quite as difficult to convince them they are celebrating something else than if an entire new day was created. For example, Easter was timed to coincide with the pagan celebration of the spring equinox.

Perhaps the secularists just figured that, if the Christians were already honoring a couple of saints on April 22nd, they wouldn't mind honoring the earth as well!

Who cares about a bunch of long-dead god-botherers?

The Earth is real, and important

And the chances are, given Christianity's rampant kleptomania (e.g. the appropriate on Easter, midwinter festivals etc), those days were previously used to celebrate some pagan festival

The Catholic Church has so many Saints Days that there is no place on the calendar that is free of them. Secularists did not steal anything; they just picked a day.

Every day is some saint or other's day. I didn't think protestants were that into saints, especially as they were canonised by the catholic church. Do any protestant denominations canonise people?