The current quarter, with a progress bar showing how much of it has elapsed. Calendar quarters are simple — three months each, starting in January — but fiscal quarters often are not, because organisations start their financial year in whichever month suits them.
Calendar quarters
Q1 January to March · Q2 April to June · Q3 July to September · Q4 October to December. This is the default meaning unless someone specifies a fiscal year.
Fiscal quarters differ
The US federal fiscal year begins on 1 October, so federal Q1 is October to December. The UK tax year begins on 6 April. Many companies pick a year-end that suits their trading cycle, which is why "Q3" is meaningless without knowing whose. The whole picture is in fiscal quarters explained.