Yeah, but you only need to get close. It’s okay if you’re off by a day or two if all you’re using it for is to decide when to plant and harvest crops.

If you’re staying in one place for a while you can set up more permanent solutions. Structures like Stonehenge have notches and openings that line up with the sun position in different seasons, so you can tell exactly which day is the solstice or equinox (or whatever days are important to you).