Current DateTime in ISO 8601 Format from the Terminal

April 11, 2020

While preparing this blog I realised that the timestamps were not automatically generated. That actually makes a lot of sense, considering the lack of database and that I’m using Gatsby, a static site generator. How would timestamps be automatically generated? At best they would be based upon commit time or something equally inaccurate, unless they’re hardcoded.

The timestamps on the template were in full ISO 8601 format, including timezone and nanoseconds.

Before I paused to tinker with other formats, I began wondering how I could automate this process.

Onward, then, to solving the problem.

I began by wondering what linux’s date would spit out. Answer: Sat 11 Apr 15:02:15 BST 2020. Good but no cigar, specifically due to the lack of timezone. Some quick Googling turned this up, with the answer I wanted:

➜  blog git:(master) ✗ date --utc +%FT%T.%3NZ 
2020-04-11T14:03:43.012Z

That was good but how was I going to remember all that? Best to store it in an alias I think.

I use Oh My ZSH! so I opened my ~/.zshrc and prepared to add the alias. As I was looking for a good spot I found this note:

Aliases can be placed here, though oh-my-zsh users are encouraged to define aliases within the ZSH_CUSTOM folder. For a full list of active aliases, run alias.

I’d never heard of that file before so had to do some digging to find it. Upon finding the file (~/.oh-my-zsh/plugins/common-aliases/common-aliases.plugin.zsh, before you ask) I saw an accompanying README, with this note:

To use it add common-aliases to the plugins array in your zshrc file:
plugins=(... common-aliases)

So, back to my ~/.zshrc file I went, made the amendment there and returned to common-alises.plugin.zsh. At the foot of the file I added these lines:

# Custom

alias current_time="date --utc +%FT%T.%3NZ"

I then reloaded my terminal:

. ~/.zshrc

And gave it a whirl:

➜  blog git:(master) ✗ current_time
2020-04-11T14:04:15.005Z

Nice!

I then finished off by realising that date: "2020-04-11" was fine, anyway. I need more cooling fluid.