Electronic calculator for date calculation
The period and number of days after (or before) the date can be calculated.
For example, the following calculations can be made.
・20 days after Jan 1 2013
・Period between Jan 1 2013 and Jan 31 2013
※ Calculated date will be a positive number if calculated using "+" and a negative number if calculated using "-".
・10,000 x period between Jan 1 2013 and Feb 1 2013 etc.