The resulted UTC date may be some milliseconds or seconds off from the actual UTC date. Unix time does not account leap seconds and all days are 86400 seconds long. UTC time does account leap seconds.
The leap seconds are guesstimated with the following equation
The guesstimated leap seconds are not added to the offset seconds. The guesstimated leap seconds are not used in the Unix epoch to UTC date conversion.
IPduh is not trying to start a new religion.
The !epoch large range is not just artistic and it may be usefull to analysts investigating incidents that happened a long time ago. The leap seconds calculation is wrong but good enough to show how the leap seconds add up with time. It assumes a constant rate at which 27 leap seconds are added every 53 years and one leap second is removed every 55 years.
Note that Unix time keeping was invented around 1970, that the leap seconds were first used around 1972, that there is not known formula for predicting the earth's speed of rotation with very high accuracy, and that we have recordings of high precision earth year duration measurements only after the invention of the cesium atomic clock.