context: When Emperor Kammu moved the capital to Heian-kyō (Kyōto), which remained the imperial capital for the next 1,000 years, he did so not only to strengthen imperial authority but also to improve his seat of government geopolitically. Nara was abandoned after only 70 years in part due to the ascendancy of Dōkyō and the encroaching secular power of the Buddhist institutions there. Kyōto had good river access to the sea and could be reached by land routes from the eastern provinces. The early Heian period (784–967) continued Nara culture; the Heian capital was patterned on the Chinese Tang capital at Chang'an, as was Nara, but on a larger scale than Nara. Kammu endeavoured to improve the Tang-style administrative system which was in use. Known as the ritsuryō, this system attempted to recreate the Tang imperium in Japan, despite the "tremendous differences in the levels of development between the two countries". Despite the decline of the Taika-Taihō reforms, imperial government was vigorous during the early Heian period. Indeed, Kammu's avoidance of drastic reform decreased the intensity of political struggles, and he became recognized as one of Japan's most forceful emperors.
question: ఎన్ని సంవత్సరాలు జపాన్ రాజధానిగా హీయాన్ ఉంది?
answers: 1,000