This change brings this bug #14 in. The date of sourceDates[date] doesn't necessarily need to be the start moment of the day. Therefore, sourceDates[date] is nil when toDate is Date().

sorry my bad

1. the dictionary was introduced because I had performance concerns.
2. you need to use Date().startOfDay as a key to archive the count for that day

I made a mistake. this pr I didn't want to introduce these changes
only

    -init(date: Date, count: Int = 0) {
    +public init(date: Date, count: Int = 0) {
        self.date = date
        self.count = count
    }

@Maples7

@racechao That's ok, I've created a PR #13 to fix these issues.

1. We can turn the [Date] into a [Date:ACData] internally with only 1 literation (O(n)) by doing so 3270273#diff-6eace7fd00e64a79f64bb279676278b16eab8ec0f93e83fa4d8f5a422ffd040b, I think the performance should be acceptable. The difference is whether we need to request users to make the conversion by themselves. And we'd better not to break the API policy for backward compatibility. Or, we can create a new init to support [Data:ACData] type parameter as the sourceDatas in the next new versions of this library.
2. Yeah the date keys have been turned into startOfDay during the process mentioned in the 1st point.

FYI @jasudev for more context.