private buildSignupForm() {
    this.SignupForm = this.fb.group({
      bday: [null, [Validators.required, Validators.maxLength(2)]],
      bmonth: [null, [Validators.required, Validators.maxLength(2)]],
      byear: [null, [Validators.required, Validators.maxLength(4), Validators.minLength(4)]],
      city: [null, [Validators.required, Validators.pattern('[a-zA-Z ]*')]],
    });
    this.SignupForm.setValidators(this.minimumAge(18));
  }
}