This is the 104th most frequent Lithuanian word.
šiandien
"Šiandien" means "today" in English.
The word 'šiandien' is used to indicate that the action or description pertains to the current day.
Šiandien oras yra labai gražus.
Today the weather is very nice.
Here 'šiandien' appears to clarify that the lack of plans concerns today's time frame.
Neturiu daug planų šiandien.
I don't have many plans today.
In this case, 'šiandien' specifies that the meeting being inquired about is intended for the current day's evening.