"Today is Thursday."
Translation:Hoy es jueves.
The temporary/permanent guideline only applies to characteristics and conditions of people. The usual mnemonic, found, e.g. at https://www.spanishdict.com/guide/ser-vs-estar is DOCTOR PLACE:
D: Descriptions (e.g. "catholic")
O: Occupations (e.g. "student")
C: Characteristics (e.g. "intelligent")
T: Time (e.g. "Hoy es jueves")
O: Origin (e.g. "Ella es de Cuba")
R: Relationships (e.g. "girlfriend")
P: Position (e.g. "seated")
L: Location (e.g. "el hotel esta alli")
A: Action (e.g. "washing")
C: Condition (e.g. "sick")
E: Emotion (e.g. "sad")
Now, what about the location of an event, such as a party? The event is bounded in time and in space. "Ser" is Lord of Time; "estar" is Lord of Space. So, both have a claim on this one. The Time Lord wins. "Ser" is used for the location of an event. The party "es" at my house.
There are other caveats, but good old Doctor Place will steer you right most of the time.