angular-ui-bootstrap-4/src/datepicker/datepicker.css

Native AngularJS (Angular) directives for Bootstrap

.uib-datepicker .uib-title {
  width: 100%;
}

.uib-day button, .uib-month button, .uib-year button {
  min-width: 100%;
}

.uib-left, .uib-right {
  width: 100%
}