The new constitution, which was approved in a public vote in March, requires a 30-day mandatory voter registration period be instituted after the approval of the new charter, experts told NewsDay Zimbabwe.
Another 56 days would be needed after the Election Day is decided until the polling date, the newspaper said. An electoral amendment bill would need to be passed before an election date can be determined.
Mugabe's signing of the constitution Wednesday effectively means planned June 29 general elections would be impossible.
The new charter sets a limit of two five-year terms for president. It increases rights for women and bans the death penalty for women, the young and elderly.
The presidential term limit wouldn't be applied retrospectively, so Mugabe, who has ruled for three decades, would eligible for another 10 years in office, NewsDay Zimbabwe reported.