$cache->renderFile doesn't cache properly when using timestamp for the expire parameter

[rastographics]

$tomorrow1AM = strtotime("tomorrow 1:00");
echo cache()->renderFile("chunks/home/birthday.php", $tomorrow1AM); 

This code works fine if I use a WireCache constant for the expire parameter. 

But if I use a timestamp, as shown above, the cache doesn't work. 
The cached does get "created" (verified by looking in TracyDebugger) with an expire time of 1am the next day. 

However, the page is still loading 1700 pages of content, and taking 800ms to execute, as opposed to 53 pages of content and 90ms to execute when the cache is correctly getting used.

So it seems that $cache->renderFile is saving the cache, but not hitting it on future loads in my case. 

Do you have any insight? Any other information I need to share?

[poljpocket]

Hard to say with this little information.

Try the following next debug steps:

1. Use any other $expire value like 3600. Does it work correctly this way?
2. Use any other file with the same $expire timestamp. Does this also produce the problem?