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Post-vacation blues (Canada and US), Post-holiday blues (Ireland and some Commonwealth countries) or just vacation/holiday blues or less commonly, post-travel depression (PTD) is a type of mood that persons returning home from a long trip (usually a vacation) may experience.
A person may suffer from post vacation blues after returning home or to a normal routine from a long vacation, especially if it was a pleasurable one. The longer a trip lasts, the more intense the post vacation blues may be. This is because after the person returns home, they realize how boring and unsatisfactory their normal lifestyle routine is when compared to the activities he or she did while on their holiday/vacation. It is easier to overcome/adjust to a normal routine the shorter the trip was. Post vacation blues may result in tiredness, loss of appetite, strong feelings of nostalgia, and in some cases, depression. Jet lag may intensify the post vacation blues.
In general, post vacation blues will wear off over time. It usually takes a few days, but in extreme cases it can last for several weeks for the mood to fully wear off. Faster ways of treating post vacation blues is for the person to share their experiences with family and friends, or to look at photos and souvenirs. Some may find comfort in re-living their holiday/vacation experiences, for example, if one really enjoyed jet-skiing during their holiday, they may purchase their very own jet-ski for personal use. Another well known method of curing post vacation blues is to plan or book the next vacation, this offers a distraction and also provides the person something to look forward to.
- Monday blues – may be experienced by persons after weekends.
- Post-holiday blues – sometimes experienced by persons after long breaks. 
- Post-party blues – may be experienced by persons after an enjoyable party or nightlife experience, not to be confused with a hangover, which can have similar psychological effects due to high alcohol intake.
- New employee apathy/Freshman apathy
- Spring fever
- Gogatsu byou/May syndrome/May diseases/May sickness/May blues(Japan)