How you write the calendar date depends on a few things, such as whether you are using British or American English. The main difference here is in the order of the elements -- think driving on opposite sides of the road. The way you write the calendar date also depends on how formal you want to be. No matter which side of the pond you live on, you wouldn't use the same style for an elegant wedding invitation that you would use on a report for work or school.
When writing the date in British English, the day comes before the month, and the year follows at the end. Think -- smaller, bigger and bigger. Makes sense.
For example, if it is the 14th of November in the year 2005, the date would be written 14 November 2005. If the day of the week is to be added, it comes at the beginning. For example, if the 14th is a Tuesday, the date would be written: Tuesday, 14 November 2005.
British English does not use commas except for separating the day of the week and the date. Plain and simple.
In American English, the month comes before the date. This too makes sense. People tend to think of a year in months.
Once again, using the 14th of November in the year 2005, American English writes the date as November 14, 2005. If you want to include the day of the week, it goes in front of the month. So it would be written as: Tuesday, November 14, 2005.
Abbreviating the Date
The order stays the same when abbreviating the date. This is a good thing for most people trying to keep track of two different calendar writing methods.
In British English, then, the 14th of November in the year 2005 would be 14/11/2005 or 14/11/05.
For American English, it would be 11/14/2005 or 11/14/05.
Rarely used in both British and American English, the year-first format can also be used to write the date.
Taking the same example -- the 14th of November in 2005 -- the date would be 2005/11/14 or 2005 November 14.
This style, when used, is mainly seen in technical writing. And it is handy for organizing a picture folder on the computer if you don't want the computer to mix pictures from various years under one month or date.
Finally, whether you are writing the date in British or American English, sometimes you may want to use the formal variations.
June 7, 2015 on a wedding invitation may be written as such: The Seventh of June, 2115 or June the Seventh, 2015.
Following the same rules for British and American calendar dates, the first example places the date first because it is British, and the second paces the month first because it is American.