There is information floating around the web that Sita was elder to Lord Rama by six months and many are quoting this to justify marrying an elder woman.
‘Though we have many examples of wife being elder than her husband in puranas, like Sita was 6 months elder than Rama, Radha was elder than Krishna and even in the case of Shiva and Shakthi according to Shakthi purana, it was Shakthi who created Shiva, Bramha, Vishnu and proposes them to marry her. But do you know who is known for, the huge difference in age among spouses?”
This information is incorrect.
Valmiki clearly declares thus, about the ages of Rama and Sita, through Sita during her conversation with Ravana when he was about to abduct her.
This is the Sloka.
mama bhartaa mahaatejaa vayasaa pa.nca vi.mshakaH || 3-47-10
aSTaa dasha hi var.hSaaNi mama janmani gaNyate | Aranya Kanda
10b, 11. mahaatejaa mama bhartaa= great resplendent my, husband; vayasaa panca vimshakaH= by age, five, twenty – twenty-five years; mama janmani= my, from birth; aSTaa dasha varSaaNi hi= eight, ten – eighteen, years, only; gaNyate= reckoned up.
“My great-resplendent husband was of twenty-five years of age at that time, and to me eighteen years are reckoned up from my birth. [3-47-10b, 11a]’
(The Shastras declare that a Man should marry a woman who is younger to him , though the ge difference is varied in different Shastras.
The important reason for this is that women age faster and become weak when compared to Men because of women giving birth to children and it is the duty of the Husband to take care of his wife during her advanced age.
And if the woman is elder to him, the problem of assisting the wife during her advanced years by the husband becomes more difficult.)
Ramayana Sloka and Translation Citation.