The time-dependent heat transfer and temperature variation of a bayonet-type thermal diode are theoretically investigated. A one-dimensional analytical model is developed to predict the dynamic behavior of the diode during heating, and a lumped-system approximation is employed for the cooling phase. Results of the analytical model and FLUENT are compared with experimental data of a bayonet thermal diode tested in Utah. Measured solar flux, ambient and room temperatures for a 24-hour period are used as the input data for the analytical model and the numerical calculation. The diode temperature variations predicted by the analytical model and FLUENT are in good agreement with experimental data. The simple analytical model is therefore capable of predicting the diode performance under real weather conditions.