openzeppelin-contracts/test/helpers/increaseTime.js

// Increases testrpc time by the passed duration (a moment.js instance)
export default function increaseTime(duration) {
  const id = Date.now()

  return new Promise((resolve, reject) => {
    web3.currentProvider.sendAsync({
      jsonrpc: '2.0',
      method: 'evm_increaseTime',
      params: [duration],
      id: id,
    }, err1 => {
      if (err1) return reject(err1)

      web3.currentProvider.sendAsync({
        jsonrpc: '2.0',
        method: 'evm_mine',
        id: id+1,
      }, (err2, res) => {
        return err2 ? reject(err2) : resolve(res)
      })
    })
  })
}

export const duration = {
  seconds: function(val) { return val},
  minutes: function(val) { return val * this.seconds(60) },
  hours:   function(val) { return val * this.minutes(60) },
  days:    function(val) { return val * this.hours(24) },
  weeks:   function(val) { return val * this.days(7) }
};

export const increaseTimeHandicap = duration.seconds(10);