How to abbreviate September 11th in English?

Sept.11

English abbreviation:

It is the abbreviation of a word or phrase to represent a complete form, which is different from the abbreviation word. English abbreviations are simple forms of English words that use important letters in English words to represent the meaning of the entire word. They are also called abbreviations.

Abbreviation of each month:

January abbreviation: Jan.

February: February abbreviation: Feb.

March Abbreviation: Mar.

Fourth month: April Abbreviation: Apr.

Fifth month: May Abbreviation: May.

June ? Abbreviation: Jun.

July: July ? Abbreviation: Jul.

August Abbreviation: Aug.

September: September Abbreviation: Sep.

October Abbreviation: Oct.

November: November Abbreviation: Nov.

December: December? Abbreviation: Dec.