June 21 is the first day of summer because it is the day of the summer solstice.
Okay, just a quick review of your high school astronomy. In summer and winter we have solstices — the summer solstice is the longest day of the year and the winter solstice is the shortest day of the year. In the autumn and spring we have equinoxes, when the day and night are the same length. So once this summer solstice passes, the days, which have been gradually lengthening since the spring equinox, will begin to shorten until the autumn equinox, after which the days will continue to become shorter and shorter and the nights longer, until the winter solstice, after which the days will begin to lengthen once again.
This is all very neat stuff. We live in a way cool universe with all kinds of interesting things to observe and learn about.
So then, should we celebrate the summer solstice?
Let’s put it another way: Is there anything wrong with a Catholic celebrating the summer solstice, or the winter solstice, or the equinoxes of spring and fall? What about the new moon, or the full moon? Would it be okay to celebrate those, to have a new moon party, for example?
The answer might surprise you.
You can celebrate anything. Celebrate the leaves falling off the oak tree in your backyard, or the first crocus of spring, or the first snow fall of winter. Celebrate sunspots or rainbows or the running of the salmon or the flowing of the sap. Celebrate the swallows returning to Capistrano or the Monarchs flying to Mexico. You are free and welcome to celebrate whatever you want.
Knock yourself out. Throw a party, have a cookout, or stay out dancing all night — go ahead — have a great time. Just don’t get confused — because no matter how much you celebrate any of these natural events, they won’t become supernatural. They won’t become sacred.
Not objectively. Objectively sacred means that something has been set apart for the worship of God; it has been hallowed.
This is why, when the Israelites entered the land of Canaan, God took the feasts of new moons and planting and harvesting and first fruits — all the things that every agrarian people on earth celebrated — and elevated them so that they became infused with sacred meaning. They pointed beyond the natural order to the saving acts of God.
Modern day “pagans” like to boast that they are restoring the sense of sacred to these natural markers of time. Wrong. By celebrating them as merely the astronomical events they are, they remove their sacred meaning. They remove the very thing that makes these natural phenomena point beyond themselves. But celebrate them if you want to.
Or you could just celebrate the feasts of the Catholic Church — truly sacred events that commemorate the saving acts of God in the history of the Church and in the lives of the saints. I’d wager that would keep you busy enough.