JavaScript

Builds 1748 and later support partial .update(). You can use it to add a sliding separator:

var slidingTimeout = null;

function showCurrentTime() {
  slidingTimeout = setInterval(function() {
    dp.update({
      separators: [{color:"Red", location: new DayPilot.Date()}]
    });
  }, 60000);  // once per minute
}

function hideCurrentTime() {
  dp.update({
    separators: []
  });
  clearInterval(slidingTimeout);
}

If there are other (static) separators in use you can mark the current-time indicator with a special property (the example below uses "currentTime" property) and copy the static separators during update:

var slidingTimeout = null;

function showCurrentTime() {
  slidingTimeout = setInterval(function() {
    var separators = dp.separators.filter(function(sep) { return !sep.currentTime; });
    separators.push({ location: new DayPilot.Date(), color: "red", currentTime: true});
    dp.update({separators: separators});
  }, 60000);  // once per minute
}

function hideCurrentTime() {
  dp.update({
    separators: dp.separators.filter(function(sep) { return !sep.currentTime; })
  });
  clearInterval(slidingTimeout);
}