The lunar calendar is often overlooked in time series data modelling, despite its importance in understanding seasonal patterns as well as economic, natural phenomena, and consumer behavior. This study aims to investigate the effectiveness of the lunar calendar in modelling and forecasting rainfall levels using various machine learning methods. The methods employed included Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) models to test the accuracy of rainfall forecasts based on the lunar calendar compared to those based on the Gregorian calendar. The results indicated that machine learning models incorporating the lunar calendar generally pro-vided greater accuracy in forecasting for periods of 3, 4, 6, and 12 months compared to models using the Gregorian calendar. These findings contributed to the advancement of forecasting techniques, machine learning, and the adaptation to non-Gregorian calendar systems, while also opening new opportunities for further research into lunar calendar applications across various domains.