To some extent, every play is displaced when it is performed outside the place or group for which it was intended. In classical drama, it is always an option to pull the play's audience back in time and to make them feel much like the original audience. But what about plays that do not reflect their own time to begin with, do not travel well, or that change radically depending on which translator, adaptor or editor gets hold of them? Displaced plays, like displaced persons, are searching for a home.
An audience comes with one set of expectations. The playwright comes with another, perhaps making choices from their imagination instead of their society. The play may be set in an era where a third set of answers exists. Sometimes the producer decides to set it in yet another time and place.
Most classical plays are also set in eras prior to their dates of authorship. The Ancient Greek playwrights were not much interested in Fifth Century Athens as source of drama. Only Aeschlus' The Persians is ‘contemporary’ to the times and only Aristophanes' satires are ‘local’. The only play that Shakespeare wrote which seems to be at all about Elizabethan daily life is The Merry Wives of Windsor. The past then, as now, seems an irresistible source of inspiration.
The time of Shakespeare and the four hundred years before him (1200 to 1600) are the most popular choices for modern writers to ‘displace’ new plays. Most of us look to these eras for our own Once Upon a Time fantasies.