period_to_seconds() approximately converts a period to seconds assuming
there are 365.25 days in a calendar year and 365.25/12 days in a month.
seconds_to_period() create a period that has the maximum number of
non-zero elements (days, hours, minutes, seconds). This computation is exact
because it doesn't involve years or months.
A numeric object. The number of seconds to coerce into a period.
A number (period) that roughly equates to the period (seconds) given.