(Bloomberg) — The most ambitious Ethereum blockchain upgrade is set to take place in September, possibly closer to the middle of the month, developers working on the project said on a conference call after what was billed as a final dress rehearsal.

The developers chose a number of so-called total terminal difficulties required of the final block mined in Ethereum before the network moved to new Software. Determining the exact date range when the upgrade will take place will require complex calculations and will be a moving target, depending on changes in network usage and support, the developers said during the call aired on YouTube Thursday. The final date range is expected to be approved in another developer call next week, though software engineers are currently looking at September 16-20.

Called the Merger, the software upgrade has been in the works for years and it will change the way Ethereum orders transactions to become more energy efficient. Instead of using power-hungry computers called miners, the network will deploy so-called validators using staked Ether tokens – a setup called proof-of-stake.

After years of delays, the timing of the merger is finally set following Wednesday’s completion of the Goerli Merger Test, which simulated the merger on a smaller scale. A few issues surfaced during the test, the developers reported on the call. Goerli’s merger, which many celebrated with YouTube-streamed parties, was the final test before the actual merger took place.

Ether is up more than 60% since dropping in June ahead of the merger move. The native blockchain cryptocurrency Ethereum rose 5.4% to $1,941 on Thursday, the highest level in two months. It traded at a record high of over $4,800 in November.

Thousands of projects and millions of investors depend on the success of the merger. The blockchain is home to over 3,400 active decentralized applications, enabling everything from gaming to trading. Ethereum holds 58% of the total $69 billion value locked in decentralized finance, which are applications for trading, lending and borrowing, according to DeFi tracker Llama.

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