Specific price with time range - bug in PS1.7.8?

[Milano2]

In newest PS 1.7.8.7 not allow to set specific price with time range (e.g: 20% discount start at 15:00 and end at 18:00. In product -> Add a specific price I can only click the from date / time and to date / time (but date also not work - after save promotions is unlimited). I found solutions on github: https://github.com/PrestaShop/PrestaShop/pull/27642 but not work in PS 1.7.8  - can someone help me and write exactly what needs to be done to fix it? I am not a programmer

 

PS 1.7.8.7
PHP 7.1