How do you write AM/PM?

This drives me crazy. I look this up all the time, and always need to check again. Why? Because there are so many options. 

list of world clocks with AM PM listings

Option One: am – pm 
• When it’s 10 pm in New York, it’s 8 am in Mumbai. 
• Tomorrow, I’m working from 9 am to 6 pm
• The meeting will be from 8 to 10 am

Option Two: AM – PM (my preference)
• When it’s 10 PM in New York, it’s 8 AM in Mumbai. 
• Tomorrow, I’m working from 9 AM to 6 PM
• The meeting will be from 8 to 10 AM

Option Three: a.m. – p.m. 
• When it’s 10 p.m. in New York, it’s 8 a.m. in Mumbai. 
• Tomorrow, I’m working from 9 a.m. to 6 p.m. 
• The meeting will be from 8 to 10 a.m. 

Spacing
When it’s 10 pm in New York, it’s 8 am in Mumbai. (space)
When it’s 10pm in New York, it’s 8am in Mumbai. (no space)
When it’s 10 pm in New York, it’s 8am in Mumbai. (don’t mix)

When it’s 10 PM in New York, it’s 8 AM in Mumbai. (space)
When it’s 10PM in New York, it’s 8AM in Mumbai. (no space)
When it’s 10 PM in New York, it’s 8AM in Mumbai. (don’t mix)

When it’s 10 p.m. in New York, it’s 8 a.m. in Mumbai. (space)
When it’s 10p.m. in New York, it’s 8a.m. in Mumbai. (no space) 

Why are there so many ways to write the time? 
It comes down to style. For example, many people feel that times like 6AM or 8PM look too strong. IT’S LIKE USING ALL CAPS! STOP SHOUTING! When we write lower case “am” or “pm”, “am” looks like the word “am”. (I am very busy today.) Similarly, many people feel using times like 6 a.m. or 8 p.m. is annoying. It looks busy, and is harder to type. 

A few tips to use the times well. 
1. Avoid using zeros for hours.
O The program is from 11 am to 5 pm. 
X The program is from 11:00 am to 5:00 pm. 

2. Use noon and midnight instead of 12:00. 
∆ The event started at 12 pm and ended at 12 am. (correct but unclear)
O The event started at noon and ended at midnight. (very clear) 

3. Avoid redundancies 
O The class will start at noon. 
X The class will start at 12 noon. 

O I woke up at five this morning. 
O I woke up at five. 
X I woke up at five am this morning. 

4. Follow your company’s style guide.
If your company prefers to use one style over the other, then you should probably do that regardless of your preference. 

For more details, take a look at these great sources:
– Western Michigan University: Writing the Time
– Proofreading Academy: AM/PM

Like this post? Did I forget something? Let me know!

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