Four Quarters

The 4–4–5 calendar is a method of telling accounting periods, and is a common calendar structure for some industries such as retail and manufacturing. It divides a year into four quarters of 13 weeks, each grouped into two 4-week "months" and one 5-week "month". The longer "month" may be set as the first (5–4–4), second (4–5–4), or third (4–4–5) unit. Depending on local customs, a week either begins or ends on Sunday – and therefore the "months" as well.