Steven,
my first guess was that your system does not know MixedUnit
- so I tried to improve the code without this command. But anyway. Here is a somewhat nicer version:
textSize = 140;
textColor = Red;
imageSize = Full; img =
Import["https://images.freeimages.com/images/large-previews/13d/xmas-decoration-1360454.jpg", ImageSize -> imageSize];
CreateDocument[
Dynamic@Overlay[{img,
secs =
Round@QuantityMagnitude[
DateDifference[Now, {2021, 12, 25, 8}, {"Seconds"}]];
days = IntegerPart[secs/86400]; secs -= days 86400;
hours = IntegerPart[secs/3600];
secs -= hours 3600;
mins = IntegerPart[secs/60];
secs -= mins 60;
Style[
TextGrid[{{days, "d"}, {hours, "h"}, {mins, "m"}, {secs, "s"}},
Frame -> None], textColor, textSize]},
Alignment -> Center], WindowSize -> Full,
WindowTitle -> "Time left until Xmas 2021"];
