Translation:In my opinion the synagogue is closed now.
No one would ever say this in English. Hours of operation are not a matter of opinion. If your knowledge of the facts is limited you'd say "As far as I know the synagogue is closed now"
I completely agree. I think it's better translated 'to my knowledge' or, as you write, 'as far as I know' . I think perhaps an Israeli might rather say 'ledaati' or some other way, I can't think exactly how, rather than lefi daati,
This is a pretty strange sentence in English--you don't normally use the word "opinion" for statements like this. I can't tell whether it's equally strange in Hebrew, or whether a better translation might be something like "I think that..." or "It seems to me that..." instead of "In my opinion...".
But it's really weird to refer to something like that as an "opinion". The hours are what they are and people don't disagree about what they are; it's not a matter of opinion but just a matter of not being sure if you're right about what they are.
It's my opinion that I am right about the facts. Your opinion is different.
If you imagine that these two people are staring at the synagogue and can't figure out if it's closed or open, the sentence might make sense. (We once showed up too early for a Purim carnival and didn't realize the place wasn't open yet).
I think this must be an instance where the nuances of the Hebrew are different enough from the nuances of the English, so that what I'm assuming is a perfectly reasonable sentence in Hebrew doesn't make sense to English-speaking ears.
Everybody is entitled to their own opinion, but not all beliefs are opinions. Assertions about facts are in a different category from preferences, value judgments or predictions about the future. When there is a disagreement about facts, it's appropriate to say "according to me" (not accepted), or "I think that" or "I believe that" or "as far as I know", but not "in my opinion".
As Snommelp said, this may be a perfectly sensible sentence in Hebrew, but the English translation just doesn't make sense.
Perhaps this should accept (at least for UK etc speakers ?)
As far as I know the synagogue is closed now
'As far as I know' should be accepted as opinion suggests an idea not a fact.
In English, "according to" is only used about secondhand sources of information, and so can't be used about yourself, by definition.
true, though the root is the same. In the CONTEXT, 'to my knowledge' would be better, and there is probably a better way to express this since 'in my opinion' doesn't really work here.