Using date picker
Date picker allows you to choose a date from a calendar pop-up window. To use date picker in Google spreadsheets, double click a cell that has a date in it.
Date picker recognizes dates with a month-day-year format if the spreadsheet locale is set to the United States. If you'd like to use date picker to format your dates as day-month-year, set spreadsheet locale to a different country (File > Spreadsheet settings...).