brotherton-erpnext/erpnext/docs/user/manual/en/customize-erpnext/custom-scripts/custom-script-examples/date-validation.md

Date Validation

frappe.ui.form.on("Task", "validate", function(frm) {
    if (frm.doc.from_date < get_today()) {
        frappe.msgprint(__("You can not select past date in From Date"));
        frappe.validated = false;
    }
});

{next}