Japanese traditional timekeeping practices required the use of unequal time units: six daytime units from local sunrise to local sunset, and six night-time units from sunset to sunrise. As such, Japanese timekeepers varied with the seasons; the daylight hours were longer in summer and shorter in winter, with the opposite at night. European mechanical clocks were, by contrast, set up to tell equal hours that did not vary with the seasons. Most Japanese clocks were driven by weights. However, the Japanese were also aware of, and occasionally made, clocks that ran from springs. Like the western lantern clocks that inspired their design, the weight driven clocks were often held up by specially built tables or shelves that allowed the weights to drop beneath them. Spring driven Japanese clocks were made for portability; the smallest were the size of large watches, and carried by their owners in inrō pouches. Traditional Japanese time system The traditional Japanese time system divided daytime and nighttime into six periods. This meant the lengths of the periods consequently change with the season. The typical clock had six numbered hours from nine to four, which counted backwards from noon until midnight; the hour numbers one, two and three were not used in Japan for religious reasons, because these numbers of strokes were used by Buddhists to call to prayer. The count ran backwards because the earliest Japanese artificial timekeepers used the burning of incense to count down the time. Dawn and dusk were therefore both marked as the sixth hour in the Japanese timekeeping system. In addition to the numbered temporal hours, each hour was assigned a sign from the Japanese zodiac. Starting at dawn, the six daytime hours were: {| class="wikitable" style="text-align:center" |- ! Zodiac sign !! Zodiac symbol !! Japanese numeral !! Strikes || Solar time |- | Rabbit || || || 6 || sunrise |- | Dragon || || || 5 || rowspan=2 | morning |- | Snake || || || 4 |- | Horse || || || 9 || noon |- | Goat || || || 8 || rowspan=2 | afternoon |- | Monkey || || || 7 |} From dusk, the six nighttime hours were: {| class="wikitable" style="text-align:center" |- ! Zodiac sign !! Zodiac symbol !! Japanese numeral !! Strikes || Solar time |- | Rooster || || || 6 || sunset |- | Dog || || || 5 || rowspan=2 |