Add the milk and pitted, soaked dates to a blender and blend until smooth.
Pour the date-milk mixture through a fine mesh strainer into a medium saucepan, then add the heavy cream, ground nutmeg, salt, and cinnamon stick.
Heat the saucepan over medium heat until hot, but do not let it boil.
In a separate bowl, mix the egg yolks and sugar together until combined.
Temper the eggs by adding 1 spoonful of the hot milk mixture at a time into the egg yolk mixture, whisking constantly. Repeat 8 to 10 times.
Pour the tempered egg yolk mixture back into the saucepan with the remaining milk. Whisk and heat over medium heat for a few minutes without letting it boil.
Pour the eggnog into a glass container to cool to room temperature, then transfer to the refrigerator to chill thoroughly.
Serve chilled with whipped cream, a sprinkle of ground cinnamon, or nutmeg. For extra warmth, stir in a dash of rum extract or spiced syrup.