Reference:
I am trying to figure out what the "Handy Time Stamp" are used for in the time package.
I can parse dates just fine using the other constants such as RFC
t, _ := time.Parse(time.RFC822, "02 Jan 06 15:04 MST")
fmt.Println(t.Unix())
Output 1136214240
vs
t, _ := time.Parse(time.Stamp, "Jan _2 15:04:05")
fmt.Println(t.Unix())
Output: -62135596800
The last output is wrong. What am I missing here? How are these timestamps useful?
Below is the Godoc for time constants:
const (
ANSIC = "Mon Jan _2 15:04:05 2006"
UnixDate = "Mon Jan _2 15:04:05 MST 2006"
RubyDate = "Mon Jan 02 15:04:05 -0700 2006"
RFC822 = "02 Jan 06 15:04 MST"
RFC822Z = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone
RFC850 = "Monday, 02-Jan-06 15:04:05 MST"
RFC1123 = "Mon, 02 Jan 2006 15:04:05 MST"
RFC1123Z = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone
RFC3339 = "2006-01-02T15:04:05Z07:00"
RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"
Kitchen = "3:04PM"
// Handy time stamps.
Stamp = "Jan _2 15:04:05"
StampMilli = "Jan _2 15:04:05.000"
StampMicro = "Jan _2 15:04:05.000000"
StampNano = "Jan _2 15:04:05.000000000"
)
The last output is wrong. What am I missing here? How are these timestamps useful?
You are definitely missing an error check here, let's add it
t, err := time.Parse(time.Stamp, "Jan _2 15:04:05")
fmt.Println(err)
fmt.Println(t.Unix())
Output:
parsing time "Jan _2 15:04:05" as "Jan _2 15:04:05": cannot parse "_2 15:04:05" as "_2" -62135596800
The correct string would be "Jan 2 15:04:05" (note the double space between Jan and 2). About underscore from the docs:
Within the format string, an underscore _ represents a space that may be replaced by a digit if the following number (a day) has two digits; for compatibility with fixed-width Unix time formats.
Then, why it's representations as UNIX time is negative, let's check:
t, err := time.Parse(time.Stamp, "Jan 2 15:04:05")
fmt.Println(err)
fmt.Println(t)
Output:
<nil>
0000-01-02 15:04:05 +0000 UTC
So it's negative because the year is 0000.
And finally, where it can be useful? For example, to measure duration of time-consuming operations. You can output to logs current time in one of Stamp formats along with some messages like "Started doing this", "Finished doing that". Then, because it's fixed-width format and without unnecessary year information - it's easy to read the logs, easy to parse such logs.
This format is actually used in "syslog" in *nix.