lastmod requires the output format to be Y-m-d

[ZhangChengLin]

sitemap/Sitemap.php

Line 259 in 17dc560

public function addItem($location, $lastModified = null, $changeFrequency = null, $priority = null)

https://github.com/samdark/sitemap/blob/master/Sitemap.php#L305
https://github.com/samdark/sitemap/blob/master/Sitemap.php#L354

Can the output format of the lastmod tag support Y-m-d
For example, if it is not an integer format parameter, let him use it directly as a string.

[ZhangChengLin]

If $lastModified is not in integer format but in string format, there is no need to format it.

[samdark]

Currently it assumes UNIX timestamp only but yeah, could be expanded to support cutom format. That adds a possibility to generate incorrect sitemap though...

[ZhangChengLin]

Currently it assumes UNIX timestamp only but yeah, could be expanded to support cutom format. That adds a possibility to generate incorrect sitemap though...

Something wrong?
why?

[samdark]

It is not wrong per se. Just need to add validation if you're going to accept strings as well. Want to make a pull request?