Time is not a "thing" itself, but a function of the fact that entities in reality demonstrate the ability to change. If certain processes take place at a consistent interval, they become useful measures of "time" which can be used to compare how long other events take. For example, one "second" is derived from the behavior of a Cesium-133 atom.

As such, it is nonsense to talk about being "outside of time", unless the system is entirely static. If there is change, there is time.

The concept of "change" becomes difficult when considering the first cause. If the first cause is one single thing, then any form of "change" is difficult to conceive of. For a change, which is basically an event in which some property of the entity changes state, to take place, there must be a "trigger" - a condition being present which initiates the conversion from "change not taking place" to "change taking place". But, a trigger always involves interactions with other things, as part of an entity's operation within a system.

For example, consider the event "an atom of gold is created in a particle accelerator". The event itself is triggered by a combination of certain atoms being in particular positions, enormous amounts of energy being present, and the properties/behaviors of atoms within our reality. Without those conditions, the event cannot take place.

But, if there is "one thing", such as is often thought to be the case when considering the first cause, there would be no system in which it is operating which can provide conditions in order for any change to take place, unless one identifies the first cause with the "trigger" simultaneously, meaning one just is the other. And that is not to say "these 2 things are being called by one name - the first cause, and a trigger, all rolled up under the term 'first cause'". It is to say that the first cause just is the trigger. But, that is very hard to make sense of, to say the least. How can "one thing" simultaneously be a property which has multiple potential states, and the condition necessary for the change of that property's state? And if the entity is not identical to the property that is being changed, then there are multiple "things" - an entity, and a property with multiple states.

Therefore, it seems likely that the first cause was not "one thing" in the absolute sense. If it were just "one thing", it seems like it would be unable to change, and "change" as it has been defined here is necessary to do anything, or perform any action.