Hola Justin

The speaker is talking in the present about an action that happened in the past, which is why we use the present perfect subjunctive.

In contrast, if the speaker were talking in the past to refer to a past action that is related to certainty in the past, then we should use the preterite, which sounds more natural. Have a look at both examples:

 Bear in mind that the use of a past time marker does not mean that the speaker cannot refer to that specific time in the present moment. In your example, he feels almost certain about that fact at this moment.

Un saludo

Silvia

Hola Weiping

En español, el tiempo verbal se llama "el pretérito perfecto de subjuntivo", por ejemplo, haya visto, hayamos ido, hayan dicho... - sin embargo, en inglés este tiempo verbal se llama "present perfect subjunctive" - la palabra "present" en el nombre inglés puede confundir un poco. 

Siempre hablamos del mismo tiempo verbal "present perfect subjunctive = pretérito perfecto subjuntivo" 

Aquí hay una tabla con los nombres de los tiempos verbales en español (España y Latinoamérica) y en inglés. 

Espero que esto aclare tu pregunta. 

Un saludo cordial.

Inma

Hola Julia

The word "pretérito" has always been "attached" to all past tenses in Spanish. At school children learn the full names as the RAE still present them. Click here and scroll down to see how they still use "pret." on their names. However, as these names are so long, we often refer to them with their shorten name, for example "el pretérito imperfecto" would be "el imperfecto" or the most common shorten name for the simple past is "el indefinido". 

As there are different names used both in Spain and Latin America, we created this table so students can get familiar with all the different names. 

Tenses names (kwiziq)

I hope this helps.

Saludos cordiales

Inma

Hola Emanuel

haya hecho could refer to I, she, he or you formal (usted); their conjugation coincides here; so the only way to know the subject is by context. 

In this sentence:

there is not enough context to know, it could be I, she, he, or you formal. 

Saludos

Inma

Hola Allison

Sentences introduced by an opinion in "negative" are followed by the subjunctive. Have a look at this lesson that will clarify your doubt:

[competency id= "6184"]

The English typo has been corrected. 

Muchas gracias,

Inma

Hi Allison

That is correct in certain cases, for example:

"Yo quiero estudiar más" (same subject in both, infinitive) but 

"Yo quiero que (tú) estudies más" (different subjects, needs subjunctive)

Also with "hope":

"Yo espero ganar la lotería" (same subject in both, infinitive) but

"Yo espero que ganes la lotería" (different subjects, needs subjunctive)

Notice the absence of "que" in the sentences with the same subject.

In order to be able to use an infinitive with "Yo no creo que..." you need to get rid of "que". For example:

Yo no creo haber hecho todos los deberes para el lunes. (although this sounds a bit formal)

With "que", the only option would be:

Yo no creo que haya hecho todos los deberes para el lunes.

Saludos

Inma

Hi Allison

Sorry about this big delay on replying to your last query. The notification didn't come through back in October. 

So, yes, this is an option too but it would sound very formal:

"Yo no creo haber hecho/terminado todos los deberes para el lunes."

Un saludo

Inma