Is it normal for my cycle length to change so drastically?

According to Glow, my periods for the past year have been 30-34 days in length. I was due to start this month on the 19th, but out of nowhere, I started today. I have NEVER had a 26 day cycle. And I usually spot for a few days before I start, and I didn't even get that. Just went straight to bleeding. Other than that, it seems normal. Normal cramping etc. so, what do you think?