Build a date picker

• A text input shows the selected date; clicking it (or its calendar button) opens a popup month grid; Escape closes it and focus returns to the input
• Previous and next month buttons and month and year headings; the grid always shows complete weeks, with days of adjacent months visually muted
• min and max props disable dates outside the range, and navigation past the limits is blocked
• A mode="range" option lets the user click a start and an end date, highlights days in between, and swaps them if the second is earlier
• Locale-aware: month and weekday names come from Intl.DateTimeFormat, and the first day of the week is configurable (Sunday or Monday)
• Keyboard: the grid uses a roving tabindex; arrows move by day or week, PageUp and PageDown by month, Home and End to the start and end of the week, Enter selects

Only after every requirement works.

• Typing a date into the input with parsing and validation
• Preset ranges such as "last 7 days"
• Disabled arbitrary dates through a predicate prop, and a "today" button