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52 lines
1.8 KiB
Markdown
52 lines
1.8 KiB
Markdown
# Format Date And Time With Time Constants
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The Go [`time` package](https://pkg.go.dev/time) has a [`Format`
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function](https://pkg.go.dev/time#Time.Format) for displaying the parts of a
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date and time in standard and custom ways. It works a bit different than you
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might be used to from other languages. Rather than using `strftime` identifiers
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like in this string `"%B %d, %Y"`, there is a canonical date that is used as a
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reference point.
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That canonical date is from Janary 2nd, 2006. That was a Monday. It was at 5
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seconds after 3:04PM. The Unix format of it looks like `"Mon Jan _2 15:04:05
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MST 2006"`.
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```
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package main
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import (
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"fmt"
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"time"
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)
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func main() {
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// This specific time pulled from `time.Format` docs
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t, _ := time.Parse(time.UnixDate, "Wed Feb 25 11:06:39 PST 2015")
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// Reference date and time:
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// "Mon Jan _2 15:04:05 MST 2006"
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strf1 := t.Format("|2006|02|01|03:04:05|Day: Mon|")
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fmt.Println("strf1:", strf1)
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// strf1: |2015|25|02|11:06:39|Day: Wed|
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strf2 := t.Format(time.DateTime)
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strf3 := t.Format(time.RubyDate)
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strf4 := t.Format(time.Kitchen)
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fmt.Println("DateTime:", strf2) // DateTime: 2015-02-25 11:06:39
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fmt.Println("RubyDate:", strf3) // RubyDate: Wed Feb 25 11:06:39 +0000 2015
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fmt.Println("Kitchen:", strf4) // Kitchen: 11:06AM
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}
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```
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Though there are a [variety of useful formatting
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constants](https://pkg.go.dev/time#pkg-constants) already available like
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`DateTime`, `RubyDate`, `Kitchen`, etc., we can also define our own formatting
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string by using the reference values for each part of a date and time.
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If you want to reference the year, whether as `YYYY` or `YY`, it is always
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going to be a form of `2006`, so `2006` or `06` respectively. Even though the
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above time variable is in February, our format strings will always need to use
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one of `Jan`, `January`, `01` or `1`.
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