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mactsouk / mGo4th

Source code for Mastering Go, 4th edition.
MIT License
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convertTimes.go from ch02 not parsing time zone correctly #1

Closed rgerardi closed 1 year ago

rgerardi commented 1 year ago

convertTimes.go from ch02 not parsing all time zones correctly.

I have not yet figured out if it's a bug with Go or something on my system but I wanted to report so you can also take a look.

For example, when I execute this program providing an input with time zones MDT, MST, PDT, or PST, it parses them as UTC. To test, I added another location for PDT time zone to check and the times should match but don't.

Example output:

$ go run ./convertTimes.go "07 October 2023 19:20 PDT"
2023-10-07 19:20:00 +0000 PDT
Current Location: 2023-10-07 15:20:00 -0400 EDT
New York Time: 2023-10-07 15:20:00 -0400 EDT
LA Time: 2023-10-07 12:20:00 -0700 PDT
London Time: 2023-10-07 20:20:00 +0100 BST
Tokyo Time: 2023-10-08 04:20:00 +0900 JST

but if I use EDT instead, it works:

$ go run ./convertTimes.go "07 October 2023 19:20 EDT"
2023-10-07 19:20:00 -0400 EDT
Current Location: 2023-10-07 19:20:00 -0400 EDT
New York Time: 2023-10-07 19:20:00 -0400 EDT
LA Time: 2023-10-07 16:20:00 -0700 PDT
London Time: 2023-10-08 00:20:00 +0100 BST
Tokyo Time: 2023-10-08 08:20:00 +0900 JST

I also noticed that using an inexisting time zone, it also parses it as UTC:

$ go run ./convertTimes.go "07 October 2023 19:20 RRR"
2023-10-07 19:20:00 +0000 RRR
Current Location: 2023-10-07 15:20:00 -0400 EDT
New York Time: 2023-10-07 15:20:00 -0400 EDT
LA Time: 2023-10-07 12:20:00 -0700 PDT
London Time: 2023-10-07 20:20:00 +0100 BST
Tokyo Time: 2023-10-08 04:20:00 +0900 JST
rgerardi commented 1 year ago

Even the example from the book doesn't work on my system:

$ go run convertTimes.go "14 December 2023 19:20 EET"
2023-12-14 19:20:00 +0000 EET
Current Location: 2023-12-14 14:20:00 -0500 EST
New York Time: 2023-12-14 14:20:00 -0500 EST
LA Time: 2023-12-14 11:20:00 -0800 PST
London Time: 2023-12-14 19:20:00 +0000 GMT
Tokyo Time: 2023-12-15 04:20:00 +0900 JST
mactsouk commented 1 year ago

This is strange – go run convertTimes.go "14 December 2023 19:20 EET" command worked OK on my system:

Current Location: 2023-12-14 19:20:00 +0200 EET
New York Time: 2023-12-14 12:20:00 -0500 EST
London Time: 2023-12-14 17:20:00 +0000 GMT
Tokyo Time: 2023-12-15 02:20:00 +0900 JST
rgerardi commented 1 year ago

This is very strange. I ran it on 2 different machines and I get the same wrong results on both. Both machines run Linux, one is Archlinux, the other is Fedora 38.

I also ran it in a container using the official Go image and I got the same wrong results. Tested both Go 1.20 and Go 1.21

mactsouk commented 1 year ago

This is on a Linux machine:

$ go run convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 19:20:00 +0200 EET
New York Time: 2023-12-14 12:20:00 -0500 EST
London Time: 2023-12-14 17:20:00 +0000 GMT
Tokyo Time: 2023-12-15 02:20:00 +0900 JST
$ uname -a
Linux thinkpad 6.5.6-arch2-1 #1 SMP PREEMPT_DYNAMIC Sat, 07 Oct 2023 08:14:55 +0000 x86_64 GNU/Linux

Can you please run a git pull to make sure that you have the latest version?

rgerardi commented 1 year ago

So strange. I just updated my Archlinux and ran a git pull. Still, same results:

$ git pull
Already up to date.

$ go run convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 14:20:00 -0500 EST
New York Time: 2023-12-14 14:20:00 -0500 EST
London Time: 2023-12-14 19:20:00 +0000 GMT
Tokyo Time: 2023-12-15 04:20:00 +0900 JST

$ uname -a
Linux vader 6.5.6-arch2-1 #1 SMP PREEMPT_DYNAMIC Sat, 07 Oct 2023 08:14:55 +0000 x86_64 GNU/Linux

$  go version
go version go1.21.1 linux/amd64

Running on a Thinkpad T14

mactsouk commented 1 year ago

On a different Arch Linux machine, I got the following:

$ go run convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 19:20:00 +0200 EET
New York Time: 2023-12-14 12:20:00 -0500 EST
London Time: 2023-12-14 17:20:00 +0000 GMT
Tokyo Time: 2023-12-15 02:20:00 +0900 JST

Maybe it is because we live at different locations. I cannot think of anything else.

rgerardi commented 1 year ago

This is too weird. And the code looks good to me but I keep getting the wrong results, no matter where I run it. More examples:

Fedora 38 Virtual Machine, running on Dell server KVM hypervisor:

$ go run convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 14:20:00 -0500 EST
New York Time: 2023-12-14 14:20:00 -0500 EST
London Time: 2023-12-14 19:20:00 +0000 GMT
Tokyo Time: 2023-12-15 04:20:00 +0900 JST

$ uname -a
Linux f38scrc01 6.5.5-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Sep 24 15:52:44 UTC 2023 x86_64 GNU/Linux

$ go version
go version go1.20.8 linux/amd64

Containers:

$ podman run -v $(pwd):/scripts docker.io/library/golang:1.21 go run /scripts/convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 19:20:00 +0000 UTC
New York Time: 2023-12-14 14:20:00 -0500 EST
London Time: 2023-12-14 19:20:00 +0000 GMT
Tokyo Time: 2023-12-15 04:20:00 +0900 JST

$ podman run -v $(pwd):/scripts docker.io/library/golang:1.20 go run /scripts/convertTimes.go "14 December 2023 19:20 EET"
Current Location: 2023-12-14 19:20:00 +0000 UTC
New York Time: 2023-12-14 14:20:00 -0500 EST
London Time: 2023-12-14 19:20:00 +0000 GMT
Tokyo Time: 2023-12-15 04:20:00 +0900 JST
rgerardi commented 1 year ago

It seems to be a known Go issue: https://github.com/golang/go/issues/63345

mactsouk commented 1 year ago

Thanks for pointing that out! Closing the issue.