time.Time initialized with time.Unix() and time.Parse() with exactly the same unix timestamp gives different results being printed with time.Format("2006-01-02")
The problem is not reproducible in playground, but I get it if I compile it myself.
My default time zone is Los Angeles, probably in different timezone result would be different.
go version go version go1.12.1 darwin/amd64
go build
./test
test.go:
package main
import (
"fmt"
"time"
)
func main() {
control1 := time.Unix(1546300800, 0)
test, _ := time.Parse("2006-01-02", "2019-01-01")
fmt.Println("control:", control1.Unix(), control1.Format("2006-01-02"))
fmt.Println("test:", test.Unix(), test.Format("2006-01-02"))
}
./test control: 1546300800 2018-12-31 test: 1546300800 2019-01-01
So unix ts is the same (1546300800), but dates are different. Why?
The printed dates are different because they have different timezones.
time.Unix() returns the local Time, while time.Parse():
Elements omitted from the value are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time).
time.Parse() returns a time.Time having UTC zone by default (if zone info is not part of the input and layout).
This also explains why you can't see it on the Go Playground: the local time there is UTC.
Printing the zone info in my local computer (CET timezone):
fmt.Println("control:", control1.Unix(), control1.Format("2006-01-02 -0700"))
fmt.Println("test :", test.Unix(), test.Format("2006-01-02 -0700"))
fmt.Println(control1.Zone())
fmt.Println(test.Zone())
Outputs:
control: 1546300800 2019-01-01 +0100
test : 1546300800 2019-01-01 +0000
CET 3600
UTC 0
If you switch both times to the same zone (e.g. UTC or local), the printed dates will be the same:
control1 = control1.UTC()
test = test.UTC()
After this, the output:
control: 1546300800 2019-01-01 +0000
test : 1546300800 2019-01-01 +0000
UTC 0
UTC 0