Sls logs --startTime not working as expected

I am having trouble using the CLI’s sls logs command, and most specifically its --startTime option when querying logs of a function (deployed on AWS).

Adding --startTime doesn’t seem to make any difference to what I get back from sls logs.

E.g.:

sls logs --stage production --function myFunc --startTime 2019-07-19

returns results from 2019-07-22 (today) only, and it is pretty much the same result without any --startTime. For sure it would be possible that the most recent logs since the 19th July are from today (22nd), but I know for a fact that this is not the case (confirmed by looking at the logs directly in CloudWatch).

My sls CLI version is 1.27.3

Not sure what I’m doing wrong, any help would be much appreciated.