The regular expression tester can be found at <a href=http://www.regextester.com/>http://www.regextester.com/</a>.  Be sure it set flags 'g' and 'm'.
<pre>

Good Three Letter Acronyms
IBM
IRS
G.M.C.


Bad Three Letter Acronyms
NASA
N.A.S.A.
IQ

<hr>
Good Times of Day
12:03
1:45
10:23pm
8:45 am
7:30 pm

Bad Times of Day
1:99
10:23pp
pm 6:30
102:345

<hr>
Good Honorifics

Mr.
Mrs.
Ms.
Dr.


Bad Honorifics
Sir
Dear
Darling
Sweety-Pookems
Bad
Id.
Mp.

<hr>
Good Numbers
1
12
12.34
123.4567
0.12334
1.23e04
4.567645e-03

Bad Numbers
45.678e09
1.2.3
12a4
4.45-e04
6.78e+-02

<hr>
Good Book Titles
<i>(A good book title has all caps, except that is of the and a & an are not capitlizes unless they start the title)</i>
A Small War of Death
Of a Small War of Death
Of Mice and Men
Alan Turing Was a Good Man
Why Students Taste Like Chicken
Is Rice White and Small
And Why is Rice White and Small


Bad Book Titles
Students eat Teachers and Other Small Rodents
and Teachers Are Smarter Than Students
is Los Vegas Really There
Why Psychos Are Bad Dates And Other Bits Of Advise
Three Important Words Are is of the and
<hr>
Good Dates
May 12, 2003
July 15, 101BC
March 14, 1AD
June 9, 1986AD
Dec 25, 4BC
Feb 14, 2009

Bad Dates
May 4th, 102BC
Jan 20, 280 anno domini
Sep 30 0ad
Apr 1, fool day
Dec 25 4BC
July 7, 20a06