Allowing the selection of calendar and calendar format
Calendars and calendar formats vary from region to region. Some are vertical in orientation, some are bidirectional, some have different starting points for the week, and some are synchronized with the moon rather than the earth's rotation around the sun. For business transactions you will find that the Gregorian calendar is the most widely used. It replaced the Julian calendar in 1752. When dealing with personal items such as birth dates, there is a greater need to support other calendar systems.
Typical calendar formats in North America follow the convention of beginning each week on the left with Sunday, then moving to the right, we would see Monday, Tuesday, and so on until Saturday. The days of the month go in a left to right and top to bottom fashion, numbering from 1 to as high as 31.
Calendars can also number from right to left, bottom to top, or top to bottom. They can also contain numerals other than Arabic digits. Arabic digit shapes are further described in Guideline C5 – Allowing the selection of cardinal number shape.
Examples of other calendar formats are noted below.
Example: The following calendar format shows a Japanese calendar for March 2007 (Heisei 19). Japan uses the Gregorian calendar but also has a solar Japanese calendar, which is simply the Gregorian calendar written in Japanese characters and including the use of an era name in addition to a numeric year. The era name of a date is derived from the name of the reigning emperor. The era name HEISEI is linked to the reigning emperor Akihito, who succeeded emperor Hirohito in 1989.
Example: The calendar format below shows a Hebrew calendar for October 2004. Israel uses both the Gregorian and Jewish calendars. The latter numbers its year from the Gregorian calendar year 3761 BC. It has 12 lunar months each regular year, and 7 leap years in a cycle of 19 years, where an extra month of 30 days is added. Thus, a regular year can have 353, 354, or 355 days, and a leap year can have 383, 384, or 385 days. For instance, the Hebrew year 5754 began on the Gregorian date September 15, 1993. Subtract 3,760 or 3,761 from the Hebrew year to get the approximate Gregorian date.
Example: The following figure shows a Thai calendar for March 1991 and the Buddhist era 2534. Thai calendars can have the last days of the month at the top, if this results in fewer rows. Thailand uses the Buddhist Era (B.E.) calendar. Countries using Buddhist calendars specify their year as the Buddhist Era, which differs from one country to another along with the recognized date of birth of the Buddha. Thailand's calendar counts its years from January 1, 543 BC, so 1994/09/30 Gregorian could be expressed as 30/09/2537 in Thailand (Buddhist Era is implicit in the context).
Generally the Gregorian calendar should be used. However, some end users may require other calendars.