1. Introduction

1. Introduction

There are a few reasons for developing this new Myanmar calendar calculation method. Firstly, we have not found any simple and precise Myanmar calendar calculation method until now. When we made literature review, some say that it is not possible to calculate the exact days for the future years in the Myanmar calendar and some say it is only possible to calculate a few years in advance. U Ohn Kyaing [Kyaing, 1964], p-290, stated "There is no method to prepare the Myanmar calendar for the future years although it is possible in the Gregorian calendar. There is no exact number to determine intercalary months and intercalary days. Years with the intercalary month can be used in the calendar only after the government has announced it. That is why, it is not possible to prepare the future years for the Myanmar calendar." Our method in this article only depends on the full moon day of Second Waso and, consequently, it is possible to calculate the future years for the Myanmar calendar. But officially announced dates still depend on the government Myanmar Calendar Advisory Board.

Secondly, the current calculation of the Myanmar calendar involves complex procedures and the understanding of difficult terms. Ancient scholars thought of not only how to calculate the calendrical days but also the ways to overcome difficulties in numerical computations. In modern days, by using a computer for calculation, we can simplify their methods by discarding the steps which were meant to make manual calculations easier. Our method only needs to know Solar Year and Lunar Month. All the calculations are based on these two constants. Precise and easy steps are mentioned clearly. We hope that this method can be used by everybody without any difficulty.

Thirdly, the efficiency and speed of the calculations are considered. About 50 years ago, U Ohn Kyaing [Kyaing, 1964], p-206, once stated "Years with the intercalary day are very difficult to determine in advance. It will cost a lot of time and money. The government Myanmar Calendar Advisory Board once tried to calculate for the future 50 years in the Myanmar calendar and it cost a lot of money." Therefore, it looks the present calculation methods requires difficult and repetitive procedures. Our method does not require any repetitive procedure and it can calculate any date of the Myanmar calendar in a few steps.

Existing Myanmar calendar calculation methods do not consider conversion from Myanmar calendar dates to Gregorian calendar dates or vice versa. In this article, we have presented bidirectional coversion between Myanmar calendar dates and other calendar dates with the equations for it.

We describe not only the algorithm but also the computer program and example calculations for the Myanmar calendar. Some of the existing Myanmar calendar programs are based on the program of Wunna Ko [Ko, 2009]. It uses Julian Day Number (JDN) to calculate the day count. But that program does not calculate whether a Myanmar year has the intercalary month or the intercalary day. Our program which is presented in this article calculates all the essential elements of the Myanmar calendar completely.

All the calculations are based on Myanmar Standard Time (UTC+06:30) which is calculated on the basis of 97° 30' longitude.