Love could be a possible theme as the title has a rather romantic feel to it.
Another theme might be the passage of time. Since it mentions the sun and the evening ('sooraj main saanjh'), it could be about how things change as the day turns into evening, perhaps in the context of relationships or life in general. It could also be about longing, as the evening can often be a time when people feel a sense of wistfulness.
I'm sorry, I'm not familiar with the specific 'tu sooraj main saanjh piyaji' story. It might be a relatively niche or regional story.
It could be a story of adventure. Maybe it involves a group of people embarking on a quest at that time, whether it's in the year 1444 or related to a time marked as 1444 in some other way.
If it's about a mom and a girl (assuming Girlferand is a girl), possible themes could be love and family. The story might focus on the mother - daughter relationship, showing how they support and care for each other.
Possible themes could be time management, as it's a story within six days. Another could be personal growth, if the character in the story experiences changes during those six days.
One possible theme could be adventure. Just think, in 44 words, one could describe a short but exciting adventure like climbing a small mountain or exploring an old attic.
Since we don't know the exact story, it could have a spiritual theme. Hindi culture has a deep spiritual side, so the story might deal with concepts like enlightenment, self - discovery, or the relationship between the mortal and the divine. It could also be a story about perseverance, showing how a character overcomes difficulties through hard work and determination.
One possible theme could be friendship. When there are 17 girls, there are likely to be many different relationships among them, and friendship could be a central theme as they support each other through various situations.
One possible theme could be family. Maybe it's about family relationships, like love, loyalty, and conflict within a family in the context of the 'perumazhakkalam' story.
There could be a theme of discovery. Maybe the train was exploring new territories, and the people on board were the first to see certain landscapes or encounter new cultures. Or it could be a theme of transformation. For instance, a person's life was completely changed because of a particular train journey. They might have met someone important, or seen something that made them change their career or life goals.
Love could be a possible theme. Many stories revolve around love, whether it's romantic love, love between friends or family. Another theme might be adventure, with a character going on an exciting journey.