Chinese Lunar Date Converter (1900-2100)

Historical accuracy in Asian cinema often hinges on the precise alignment of events with the Lunisolar calendar. Films like Chang An or The Wandering Earth rely on specific festival dates and solar terms that do not align linearly with the Gregorian system. Researchers and enthusiasts frequently encounter confusion when translating dates from historical records or plot points rooted in the 60-year stem-branch cycle. This utility provides bidirectional conversion spanning 1900 to 2100. It accounts for the complex intercalation of leap months, which occurs approximately every 719 years, ensuring that festivals like the Spring Festival or Dragon Boat Festival are pinned to their correct historical context.

The calculation relies on the astronomical positions of the sun and moon. A lunar month is defined by the interval between two new moons, averaging 29.53 days. Consequently, a lunar year is roughly 11 days shorter than a solar year. To maintain synchronization with the seasons, a leap month is inserted based on the 24 Solar Terms. Errors in date conversion often lead to anachronisms in film criticism or misunderstandings of plot timelines dependent on seasonal agriculture.

The Lunisolar calendar synchronization relies on the Metonic cycle. The relationship approximates that 19 tropical years are nearly equal to 235 synodic months. This is expressed as:

To determine if a year Y has a leap month, astronomical data regarding the Solar Terms is consulted. The gap between the solar and lunar year is calculated as: