use RFC3339 `CreatedAt` time format in `docker compose ps --format=json` output

[trim21]

Description

Description

Normally in json we use RFC3339(Nano) time format in json but in current output of json output it's "CreatedAt":"2025-02-02 08:40:17 +0000 UTC", which is a very "strange" format.

Steps To Reproduce

No response

Compose Version

Docker Compose version v2.28.1

Docker Environment

Anything else?

how to do this:

diff --git a/cmd/formatter/container.go b/cmd/formatter/container.go
index f1eb47caf5..13e7708560 100644
--- a/cmd/formatter/container.go
+++ b/cmd/formatter/container.go
@@ -183,7 +183,7 @@ func (c *ContainerContext) Command() string {
 }
 
 func (c *ContainerContext) CreatedAt() string {
-	return time.Unix(c.c.Created, 0).String()
+	return time.Unix(c.c.Created, 0).Format(time.RFC3339Nano)
 }
 
 func (c *ContainerContext) RunningFor() string {

[ndeloof]

We use the same formater as docker/cli for consistency
https://github.com/docker/cli/blob/master/cli/command/formatter/container.go#L199

This is used targeting a human reader, not adequate for json output indeed.

Changing this would be a backward compatibility break and require synchronous change in both docker/cli and compose. I guess this would be risky for a minimal benefits.

[trim21]

sorry, I'm only proposaling to change format in json output but not outout in docker/cli or table format.

The example patch may change output of text format but that's my mistake, I'm not proposing to change anything except json output.

[ndeloof]

sure, but this is still a breaking change.

[ndeloof]

Closing this issue as "not planned".
We could support this if https://github.com/docker/cli/blob/master/cli/command/formatter/container.go#L199 offers a mechanism to opt-in for RFC3339 date format (feel free to open an issue on docker/cli)