A time period established by a statute, other legal acts, or a transaction or designated by a court shall be determined by a calendar date or the expiration of a time interval that is calculated in years, months, weeks, days, or hours. A time period may also be determined by an indication of an event that must inevitably occur.

The running of a time period defined by a time interval starts on the day after the calendar date or the occurrence of the event that defines its beginning.

A time period calculated in years shall expire on the corresponding month and day of the last year of the time period. The rules for time periods calculated in months shall be applied to a time period defined as a half-year.

The rules for time periods calculated in months shall be applied to a time period calculated by quarters of a year. In such a case a quarter shall be considered as equal to three months and counting of quarters shall be done from the start of the year.

A time period calculated in months shall expire on the corresponding date of the last month of the time period. If the end of a time period calculated in months falls in a month in which there is no corresponding date, then the time period expires on the last day of this month.

A time period defined as a half-month is considered as a time period calculated by days and is considered equal to fifteen days. A time period calculated in weeks expires on the corresponding day of the last week of the time period.

 If the last day of a time period falls on a non-work day, the day of ending of the time period is considered to be the next work day following it.

The source: iravaban.net