Learn Russian: Вечер был длинный.

In Russian, the past tense verb changes to match the gender of the subject. The word вечер (evening) ends in a consonant, meaning it is a masculine noun. Therefore, we must use the masculine past tense form был.

Why does the word for long end in -ый (длинный)?

Adjectives must match the gender of the noun they describe. Since вечер is masculine, the adjective takes the standard masculine ending -ый. If we were describing a feminine noun, like ночь (night), it would change to длинная.

If I wanted to say 'The evening IS long' in the present tense, would I still use a verb?

No! In the present tense, Russian drops the verb 'to be'. You would simply say Вечер длинный (literally 'Evening long'). You only need to use был to show that this happened in the past.

If I want to add a past time word like вчера (yesterday) to this sentence, where should I put it?

Russian word order is very flexible. You can put it at the very beginning (Вчера вечер был длинный) to set the scene right away, which is the most common choice, or you can place it at the end (Вечер был длинный вчера).