Should the verb be singular or plural in this sentence: "The 1830s were a time" versus "The 1830s was a time"?
The 1830s were a time of great difficulty.
Any decade includes 10 years (here 1830-1839) so use the plural.
I won't swear this is technically correct, but since you put an "s" after 1830, I think most people would use a plural verb anyway.
If you wrote something like:
The last decade was very positive for us.
then use the singular.