| Variation type | Achievement time periods (could be multi-choices) |
| Periodical daily variation | In the morning (from 6:00 to 10:00) |
| In the noon (from 10:00 to 14:00) | |
| In the afternoon (from 14:00 to 18:00) | |
| In the evening (from 18:00 to 22:00) | |
| In the midnight (from 22:00 to 2:00) | |
| In the dawn (from 2:00 to 6:00) | |
| Periodical seasonal variation | Summer (from June to August) |
| Autumn (from September to November) | |
| Winter (from December to February) | |
| Spring (from March to May) | |
| Sequential variations | Every hour |
| Every day | |
| Every week | |
| Every month | |
| Every year | |
| Sudden variations | Along with big events (earthquakes, floods,…) |
| Along with medium events (sudden pollutants, peak periods,…) | |
| Along with small events (sudden light, noise, dust,…) |