Determining the date of maturity or due date?

To illustrate, the due day of 90 day note dated March 16 maybe determined as follow:

Term of the note ...........................................90

March(days).....................31

Date of note ....................16

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Remainder days in March........15

April (days).............................30

May(days)...............................31

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Total...................................................................76

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Due date, June..................................................14