What is 999999999999ULL I am building an altcoin based on bitcoin 0.12, in chainparams we find :

consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 0;
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 999999999999ULL;
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 0;
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 999999999999ULL;


what is 999999999999ULL?
should I use it in mainnet parameters instead this old dates ?

   consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008

// Deployment of BIP68, BIP112, and BIP113.
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1456790400; // March 1st, 2016
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017


Thanks
These values appear for the regtest chain only.

It looks like these values are supposed to state the time window during which deployment of a particular protocol change is allowed to happen. For regtest that window is set to be from times 0 to 999999999999, maybe so that you can do it whenever you want.

For your coin, you presumably either want these features active from day 1, or not at all. In either case you'll probably want to remove the time-deployment code altogether.