In the Shiva purana it is mentioned that Sati went to see Rama. Is this a form of time travelling to the future as Rama did not exist when Sati was alive?
No, there is no time travel involved. It just just that Shri Rama descended on earth multiple times, one of them being at the time of Sati. Below we will discuss the timeline of the current Svetavaraha Kalpa.
Firstly let’s see, Sati’s timeline. Daksha was born in Swayambhuva Manvantara of current Svetavaraha Kalpa (yes current unlike what is said elsewhere):
The current Kalpa is named Vārāha. O excellent brahmins, in this Kalpa the Manus are fourteen in number. Among the Manus, Svāyambhuva and others constitute the first seven Manus, Sāvarṇika and others constitute the next seven. Among them Vaivasvata Manu is the seventh.
-Shiva Purāṇa, Vāyavīya-saṃhitā, Chapter 11.7
Lord Dakṣa begot of Prasūti, the daughter of Svāyambhuva, twenty-four daughters called the mothers of the world. (Verse 9) Dakṣa’s daughter Satī, wife of Rudra cast off her body as daughter of Dakṣa in the context of the insult offered to her husband. (Verse 17-18)
-Shiva Purāṇa, Vāyavīya-saṃhitā, Chapter 17
And thereafter, Shiva Parvati are reunited in the period before the current Vaivasvata Manvantara itself, as is evident from the the chapter following the next.
The same is also verifiable from the Brahmanda Purāṇa Anuṣaṅga-pāda Chapter 13. The incidents in these two are very clear unlike other Puranas where several questions can be raised.
Timeline of Shri Rama
The Ramayana that we know occurred in the 24th Treta Yuga of the current Vaivasvata Manvanatara. However, as discussed here, the descent of Shri Rama on earth has happened many times, and Tulsidasji has mentioned reasons for about five of them in the Sri Ramcharitmanas. I’m talking of the 2 which will help us solve the question.
- The one we currently know as it occurred in the 24th Treta of the present Vaivasvata Manvantara, happened owing to the curse of Jaya Vijaya where Kashyapa and Aditi (Rishis of Vaivasvata Manvanatara) became Dasharatha and Kausalya:
There were two beloved doorkeepers of Hari, Jaya and Vijaya known by everyone.....once for their sake, the one kind towards his devotees took on a body.
-RCM Balakanda Doha 122-123
When this Ramayana of the 24th Treta of the Vaivasvata Manvanatara happened, Shiva Parvati were already married, (as stated above) which can also be verified by the fact that Sitaji is requesting Devi Parvati to grant Shri Rama as a husband in RCM. There is no meeting with Sati here in the Vaivasvata Manvantara.
- The Ramayana that happened in the Swayambhuva Manvanatara, or soon after is the one we are concerned with. Being of the Swayambhuva Manvanatara or soon after, the reason for descent to earth was obviously linked to Swayambhuva Manu and Shatarupa performing penance to get Shri Rama as their child (RCM Balakanda 142-152). It is at this time when Shri Hari descended on earth that Sati had Visvarupa Darshanam of him and Sitaji and the fact is described by Lord Shiva as:
The Lord whom you, in the body of Sati, saw roaming in the forest along with his brother, in the garb of an ascetic, and seeing whom you became so afflicted, that the effect has still not worn off. Hear this character oh Bhavani. ... Swayambhuva Manu and Shatarupa from whom a wonderful creation took place....
-RCM Balakanda 141.2-3, 142.1
The timelines mentioned in the RCM are in accordance with the Puranic timeline as mentioned above. There is no discrepancy. Ramayana happened multiple times.
From the above we can see that Sati’s timeline coincides with the Rama Leela that occurred in the Swayambhuva Manvantara (or soon after). There was no time travel by Sati to meet Shri Rama in the Ramayana of the current Vaivasvata Manvantara.
Note: Although the RCM uses the word ‘kalpa’ to denote the many times Bhagavan descended on earth, it must be understood as ‘Manvanatara’ and of the current Svetavaraha kalpa only. Reason and basis: It seems sometimes these terms are used interchangeably, as done in the case of the type of Pralaya described at the time of Manvanatara change during Matsya Avatara is also called as Kalpanta Pralaya in many Puranas. Hence here it would be wise to consider the term Kalpa used in RCM as meaning Manvanatara.