Add Determining The Age Of Things as a postgres til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_415 TILs and counting..._
+_416 TILs and counting..._
 
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@@ -191,6 +191,7 @@ _415 TILs and counting..._
 - [Day Of Week For A Date](postgres/day-of-week-for-a-date.md)
 - [Default Schema](postgres/default-schema.md)
 - [Defining Arrays](postgres/defining-arrays.md)
+- [Determining The Age Of Things](postgres/determining-the-age-of-things.md)
 - [Dump And Restore A Database](postgres/dump-and-restore-a-database.md)
 - [Edit Existing Functions](postgres/edit-existing-functions.md)
 - [Escaping A Quote In A String](postgres/escaping-a-quote-in-a-string.md)

postgres/determining-the-age-of-things.md

@@ -0,0 +1,27 @@
+# Determining The Age Of Things
+
+In PostgreSQL, we can determine the age of something (or someone) by passing
+a timestamp to the `age` function.
+
+For instance, if we want to know how long it has been since y2k, we can run
+the following query:
+
+```sql
+> select age(timestamp '2000-01-01');
+           age
+-------------------------
+ 16 years 4 mons 12 days
+```
+
+Additionally, if we want to know the amount of time between two dates, we
+can pass two timestamps to the `age` function.
+
+For example, we can find out how old Prince lived to be by passing in the
+date of death and then date of birth:
+
+```sql
+> select age(timestamp 'April 21, 2016', timestamp 'June 7, 1958');
+           age
+--------------------------
+ 57 years 10 mons 14 days
+```