Calendar help!!!

Brittany • Brittany • 24 • Tom is my saving grace. I love you <3 6.30.14 <3
Got my period the 22nd this month
Calendar says I'm due 21st of April...
My cycle length is 28 days why is it showing my cycle as 31/32 days. This has been happening the last 2 months now... My period is slightly irregular by 1 or 2 days only but that's rare...
How do I fix this?