The cycle date is when your statement's billing period ends (also known as a statement closing date). When your statement cycles, this generates your billing statement.
The date can vary slightly from one month to the next. The reason for this variance is because statements won't close on a weekend or holiday.

The account cycle is the range of dates your billing period starts and ends. It's approximately 30 days long.
The reason an account cycle isn’t a fixed number of days is because the statement cycle date isn’t fixed. Which causes the number of days in each cycle to vary.