For example, if you wish to remember the 1980s, you would write '80s with an apostrophe in place of the 19 and a S at the end...
When shortening a decade, place an apostrophe before the digits (facing the proper way), but NOT before the "s." Nothing can be possessed by a decade! Decades are forms that function as units of measurement as well as quantities by themselves.
So, the answer is to write a '10' sign. Now, if you want to write the actual decade, then write it like this: 1960's. Or 1920's.
Years are a good time to use an apostrophe. When missing numerals, an apostrophe, like a contraction, should be used with caution. If you're referring to the 1950s, you might omit the first two digits and just say "the '50s." If you mean the year 2000, then you need to write it as two words: "the year 2000." Using an apostrophe in this way is common when writing dates.
Years after 1900 can also be written as two words if they are part of a name or title: "the Mr., Mrs., Miss, or Ms. Year." This is especially common with students or employees who hold multiple titles over their lifetime. For example, Charles Darwin was called "Mr. Darwin" during his life. After his death, he became known as "The Father of Evolution," so people started calling him "Dr. Darwin" instead.
Years before 1900 must always be written as one word: "the '16os."' This is because there are only four letters after 1900; we don't have enough space to write out the full form of years before then.
There are three ways to indicate a single-digit year: a hyphen, a leading zero, or an apostrophe. A single-digit year that refers to a specific year within our current century uses a leading zero, such as "1999".
The right sign for abbreviating the year with two digits, according to this source, is an apostrophe: When shortening a year, leave off the first two numerals and denote the omission with an apostrophe: 2009 becomes '09 (rather than '09). 2010 is renamed '10' (rather than '10). Thus, '06'st means sixth and '07'st means seventh. An apostrophe is also used in words that end in -y, such as apathy.'05'st means fifth.
When shortening a year, leave off the first two numerals and denote the omission with an apostrophe: 2009 becomes '09 (rather than '09). 2010 is renamed '10' (rather than '10). If we're still living, 2525 becomes '25. 2626 becomes '26.
There are several words that include this practice for renaming years: last year, next year, former year, previous year. These words use the apostrophe to indicate that something has been taken away or omitted.
Apostrophes are also used in science experiments to show what was left out of the experiment: 'naked mice', 'dyed sheep'. In mathematics, you will sometimes see the word 'apostrophe' used as a term for "the mathematical symbol that means 'in place of'" or "instead of': 'a hot day replaced by a cold one'."
In linguistics, the apostrophe is used to indicate the loss of a letter or letters during language evolution. For example, old English used to be written as one word: h-e-l-l-o. To make a y sound, people dropped their h's until only three sounds remained: e, l, and o. These three sounds were all made using the uvular cavity below the tongue. So, to make a y sound, they pulled back the tongue and exposed the uvula.
Except at the start of a phrase, years should be stated as numbers. Most style guides agree that beginning a sentence with a numerical is bad form, hence years should be spelt out as words at the start of a phrase. This is especially important when writing about astronomical dates - 2001 was an awesome year.
Words can be used instead if this is preferred but only experts will understand such usage.
Years can also be expressed as sentences to make them sound more important. For example, "years ago" or "years!"
Months and days are always written as words, except at the end of a sentence or in an abbreviation.
There are three types of date: explicit, implicit, and ordinary.
An explicit date is given as day/month/year. An example would be "March 24th". There are two problems with this format. First, it's hard to read. Second, it doesn't tell you what time it is. If you don't know, then how will anyone else? So most people choose to include the time too. This makes the format day/month/year h:mm. Examples include "April Fools' Day" and "October 31st."
Implicit dates rely on context to give information about the time.
Using apostrophes with dates: Although it may appear strange to have a number and a letter next to each other without punctuation, the plural does not contain an apostrophe. Thus, the date's year, month, and day all require an's' suffix.
This is because dates are counted numbers. There are only 365 days in 2010, not 366. Also, there are 12 months in a year, not 13.
Dates are used to describe events that took place during a particular period. So, by extension, they also describe things that happened on certain days or months.
For example, the first date we find for Jesus is the crucifixion. Before then, there are no recorded events called "the crucifixion". But once it was done, it became part of Christian history and worship, so a writer using words as we do today would know how to end a sentence with a date: "The crucifixion took place on April 10, 30 AD."
Also, before there were calendars to help people keep track of the seasons, people used to count time by events that took place on specific days. So, too, with Christians. They don't just remember what day it is on any given date, but which day of the week and month it is as well.
When reducing 2012 to just '12, use an apostrophe. That adaptable punctuation mark (seen at left, a strong one being appropriately employed) fills in for missing numbers just like it does for missing letters in a contraction. It may also be used for decades! So, yes, you can write that he's been dead twenty years.