material-components/material-components-android · error · IllegalArgumentException

current Month cannot be after end Month

Error message

current Month cannot be after end Month

What it means

The companion check in CalendarConstraints: when openAt is non-null and openAt.compareTo(end) > 0, the opening month is past the upper bound and the constructor throws IllegalArgumentException. Together with the start check it enforces start <= openAt <= end, preventing a picker that opens outside its own selectable range.

Source

Thrown at lib/java/com/google/android/material/datepicker/CalendarConstraints.java:77

  private CalendarConstraints(
      @NonNull Month start,
      @NonNull Month end,
      @NonNull DateValidator validator,
      @Nullable Month openAt,
      int firstDayOfWeek) {
    Objects.requireNonNull(start, "start cannot be null");
    Objects.requireNonNull(end, "end cannot be null");
    Objects.requireNonNull(validator, "validator cannot be null");
    this.start = start;
    this.end = end;
    this.openAt = openAt;
    this.firstDayOfWeek = firstDayOfWeek;
    this.validator = validator;
    if (openAt != null && start.compareTo(openAt) > 0) {
      throw new IllegalArgumentException("start Month cannot be after current Month");
    }
    if (openAt != null && openAt.compareTo(end) > 0) {
      throw new IllegalArgumentException("current Month cannot be after end Month");
    }
    if (firstDayOfWeek < 0
        || firstDayOfWeek > UtcDates.getUtcCalendar().getMaximum(Calendar.DAY_OF_WEEK)) {
      throw new IllegalArgumentException("firstDayOfWeek is not valid");
    }
    monthSpan = start.monthsUntil(end) + 1;
    yearSpan = end.year - start.year + 1;
  }

  boolean isWithinBounds(long date) {
    return start.getDay(1) <= date && date <= end.getDay(end.daysInMonth);
  }

  /**
   * Returns the {@link DateValidator} that determines whether a date can be clicked and selected.
   */
  public DateValidator getDateValidator() {
    return validator;

View on GitHub (pinned to ac7e18efee)

Solutions

1. Clamp openAt to the bounds before building the constraints.
2. Omit setOpenAt entirely when there is no trustworthy value; the picker picks a default month within bounds.
3. Re-validate restored selections against current start/end before feeding them back.

Example fix

// before
val constraints = CalendarConstraints.Builder()
    .setEnd(endMonth)
    .setOpenAt(Today) // Today > endMonth -> throws
    .build()

// after
val openAt = if (todayMonth > endMonth) endMonth else todayMonth
val constraints = CalendarConstraints.Builder()
    .setEnd(endMonth)
    .setOpenAt(openAt)
    .build()

fun clampOpenAt(openAt: Month?, start: Month, end: Month): Month? = when {
  openAt == null -> null
  openAt > end -> end
  openAt < start -> start
  else -> openAt
}

val constraints = CalendarConstraints.Builder()
    .setStart(start).setEnd(end).setOpenAt(clampOpenAt(saved, start, end)).build()

When it happens

Trigger: Builder().setOpenAt(month) with month after setEnd(month); computing openAt from 'today' while end is capped in the past (e.g. birthdate picker with end = today - 18y and openAt defaulting to today); restoring an old selection newer than a tightened end bound.

Common situations: Date pickers with future dates disallowed (end = today) combined with an openAt computed from a previously selected future date; symmetric to the start violation and appears in the same state-restoration flows.

Related errors

• start Month cannot be after current Month
• firstDayOfWeek is not valid
• Only Gregorian calendars are supported.
• There must be a keyline marked as focal.
• No color resources provided for harmonization.

AI-assisted analysis of material-components/material-components-android@ac7e18efee (2026-08-14). Data as JSON: /api/errors/0c7de5f9a05ed973. Report an issue: GitHub.