* Returns the number of milliseconds in the specified, years, months, weeks, days, hours, minutes and seconds.
*
* @description
* Returns the number of milliseconds in the specified, years, months, weeks, days, hours, minutes and seconds.
*
* One years equals 365.2425 days according to the formula:
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* > Leap year occures every 4 years, except for years that are divisable by 100 and not divisable by 400.
* > 1 mean year = (365+1/4-1/100+1/400) days = 365.2425 days
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* One month is a year divided by 12.
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* @param {Duration} duration - the object with years, months, weeks, days, hours, minutes and seconds to be added. Positive decimals will be rounded using `Math.floor`, decimals less than zero will be rounded using `Math.ceil`.