Verb following que: Past/Present vs Present Subjunctive
 

Hi,

Is there any rule of thumb about when in an essentially "indicative" sentence subjunctive is required after que?

For example, I understand why

Que disfrutes de tus vacaciones

but why

Y no me creo que lleve diez días fuera

?

That is, I see a lot of sentences that look for me just like the last one with past or present after que. No subjunctive. It is not really an arbitrary choice, or is it?

Whether the subjunctive is used in colloquial speech is ALWAYS based on how the speaker feels. Because of this, it can seem arbitrary, but it never is. The speaker's attitude toward the idea is what is important.

Rules for proper subjunctive usage exist. They are well defined, in fact.
It has been the topic of many a thread in the forums, since the subjunctive is rarely used in American English.

Anything that doesn't seem real conveys denial or doubt. Emotions, wishes/desires, requests, and impersonal expressions (like sentences that start with 'que' or ojalá) dictate the use of the subjunctive mood.
Look up when to use the subjunctive mood by searching for 'WEIRDO' online.

The sentence you understood is an impersonal expression (an impersonal wish, if you will). It can easily be changed to a personal wish by including a conjugated form of 'esperar' prior to the conjunction 'que'. Espero que disfrutes de tus vacaciones.
Wishes do not deal with real events.

The second sentence has a negated verb in the main clause. If you don't believe something, it isn't a real event in your mind. You either doubt it or are in denial about it; therefore, it can only be dealt with by using the subjunctive mood.

The present subjunctive is used when the verb in the main clause is in the present or future tense.
A past tense verb or a conditional mood verb in the main clause calls for the use of the past subjunctive in the secondary clause.

I agree with Rusty. The "rule of thumb" is that negative statements with two verbs often ;) need this construction.
- Creo que no está en casa. / No creo que esté en casa.
- Dice que va a trabajar. / No dice que vaya a trabajar.
- Oigo que me llaman. / No oigo que me llamen.
- Veo que llueve. / No veo que llueva.
- Pienso que ya lo sabe. / No pienso que ya lo sepa.

How fascinating! Thanks a lot!