Keyboard support
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The datepicker includes some keyboard navigation:

up, down, left, right arrow keys
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By themselves, left/right will move backward/forward one day, up/down will move back/forward one week.

With the shift key, up/left will move backward one month, down/right will move forward one month.

With the ctrl key, up/left will move backward one year, down/right will move forward oone year.

Shift+ctrl behaves the same as ctrl -- that is, it does not change both month and year simultaneously, only the year.

escape
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The escape key can be used to hide and re-show the datepicker; this is necessary if the user wants to manually edit the value.

enter
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When the picker is visible, enter will simply hide it.  When the picker is not visible, enter will have normal effects -- submitting the current form, etc.