The Hijri calendar is the calendar that is relied upon by Muslims in determining the day, month and year, and depends on the circulation of the moon. The beginning of this calendar originates from the Hijrah, namely the migration of the Prophet Muhammad SAW from Mecca to Medina which occurred in 622 AD.As for the Gregorian calendar, it is the calendar that most of the world relies on, and it relies on solar cycles. The start date of this calendar is from the time of Jesus Christ, peace be upon him, which Christians consider the beginning of a new era after the birth of Christ.The method of calculating the year, month and day differs between the Hijri calendar and the Gregorian calendar, and dates can be converted from one calendar to another using the tables defined for them.The Hijri and Gregorian calendar application is an application that allows users to find out dates in both the Hijri and Christian calendars. This application contains a series of useful features that help users keep track of important events and events in their life.Among the keywords used in this application: Hijri Calendar: This is the calendar that Muslims follow and is based on the moon, and consists of 12 months. Gregorian calendar: This is the calendar that most of the world follows and is based on the sun, and also consists of 12 months. Converting between two calendars: This application allows users to convert between two calendars easily and quickly, so that they can view the date on either calendar at any time. Religious events: This application includes the dates of important religious events in both the Hijri and Gregorian calendars, such as the month of Ramadan, Eid al-Fitr and Eid al-Adha. Public Events: The app also lists the dates of public events and important events on each calendar, such as public holidays, school holidays and sporting events.In short, it can be said that the Hijri and Gregorian calendar app is a useful application which helps users to follow important events in their life and find out the dates in each of the two calendars easily and effortlessly.