EOT Not Correctly Generated

I have our membership signup page set up with the following PHP code:

[php]
$now = strtotime(‘now’); // The time now (in seconds).
$fixed_eot_time = strtotime(’+1 year 1 Oct’); // Future time (in seconds).
$days_until_fixed_eot_time = round(($fixed_eot_time - $now) / DAY_IN_SECONDS);
// ↑ This is where we calculate the number of days until an EOT should occur.
[/php]

The EOT is supposed to be Oct 1 the following year. This worked perfectly until the last two members joined and the EOT was 10/22/18 and 10/21/18. Not sure why this is happening – recent update? Thanks so much for any help!