I'm a journal-er. I have tons of journals but I also have calendars from years past. Recently I went back through them because I was seeing signs of daylilies appearing right here the first week of January. I thought that was a bit strange till I went back to '94 where I'd written on April 22 that my first daylily bloomed.
That's not an important date, dates of last frost and dates of planting vegetables, etc., are vital statistics. But, being the visual that I am, I can tell you the exact daylily that bloomed on April 22, 1994. It isn't the first one that blooms every year, but I can look at the calendar comment and I remember the old red noid daylily that was planted in the SW side of my house in the corner beside the deck and the water spigot.
Calendars are great, but hoarding them from the early 90s is probably rather ridiculous.
And BTW, my daylilies rarely start their blooming parade before the last of May. I failed to remember or to write down the weather pattern that year.
Great tip, Song!