According to Official Guinness Records,
The most contributions to a computer program in 24 hours is 806, achieved by Avanade Inc., in Houston, Texas, USA, on 20 October 2016. This attempt was done at the 2016 Grace Hopper conference that celebrates women in technology and computing, at the George R. Brown Convention Center.
For a complete list of 2016 records, please visit 2016 Guinness Records in United States.