日付にマッチする regex pattern

"2020/12/11 03:45:56.005".matches(
    "2[0-1][0-9][0-9]/[0-1][0-9]/[0-3][0-9] [0-2][0-9]:[0-5][0-9]:[0-5][0-9]\\.[0-9][0-9][0-9]"
)