Google intends people to use Google Photos as a repository for more or less every photo they've ever taken. It works great in that regard (assuming you don't mind paying up for the best quality), but if you're a shutterbug, you'll quickly find your account filling up with thousands of photos.
Google has a lot of different ways to find them, many powered by its server-side image processing. But if you happen to know what day or month your photo was taken, there's an easy way to go right to it. Just put the date in the search bar, and Photos will immediately return photos taken and uploaded to your account on that day. The search string works in the month-day-year (8-1-2019) format for me, but I'm in the US—it might be different elsewhere.
It's a perfect way to find photos from birthdays, holidays, et cetera. The same date string search will work on the web version of Photos, as well as the iOS app.
