espocrm-base/application/Espo/Resources/metadata/app/dateTime.json

{
    "dateFormatList": [
        "DD.MM.YYYY",
        "MM/DD/YYYY",
        "DD/MM/YYYY",
        "YYYY-MM-DD",
        "DD. MM. YYYY"
    ],
    "timeFormatList": [
        "HH:mm",
        "hh:mma",
        "hh:mmA",
        "hh:mm A",
        "hh:mm a"
    ]
}