wrong date in php script

In my php script set the field "purchase_date" with the current date:

date('d-m-Y h:i:s a', time());

but this will set 0006-09-08 09:46:49 in the custom field, why? this code return:

01-03-2018 01:07:12 pm

so why not working?

LimeLM is trying to "fix" your malformed input. Date/Time values must be in the form YYYY-MM-DD hh:mm:ss

See: https://wyday.com/limelm/help/license-features/#add-new-types