php 시간 관련 함수

date
strtotime
strftime

참고

• https://www.w3schools.com/php/func_date_date_format.asp
• https://unikys.tistory.com/272
• https://mytory.net/php/2015/01/19/strftime.html
• https://www.php.net/manual/en/function.strftime.php