Update timestamp and data only if user opened chart on "current time"

[scsirdx]

There can be 2 cases for displaying a chart:

• user opened chart on some previous date -> we don't need to update timestamp in background, because this will rewind chart to current time. And we don't need to update data in background.
• user opened chart on current hour/day/month/year -> we need to update data in background (#23) and update timestamp if current date passed threshold (hour/day/month/year).