A few centuries ago, dating was sometimes described as a ""courtship ritual where young women entertained gentleman callers, usually in the home, under the watchful eye of a chaperone ,""  but increasingly, in many Western countries, it became a self-initiated activity with two young people going out as a couple in public together. Still, dating varies considerably by nation, custom, religious upbringing, technology, and social class, and important exceptions with regards to individual freedoms remain as many countries today still practice arranged marriages, request dowries, and forbid same-sex pairings.
Although in many countries, movies, meals, and meeting in coffeehouses and other places is now popular, as are advice books suggesting various strategies for men and women,  in other parts of the world, such as in South Asia and many parts of the Middle East, being alone in public as a couple with another person is not only frowned upon but can even lead to either person being socially ostracized. In the twentieth century, dating was sometimes seen as a precursor to marriage but it could also be considered as an end-in-itself, that is, an informal social activity akin to friendship.
It generally happened in that portion of a person's life before the age of marriage,  but as marriage became less permanent with the advent of divorcedating could happen at other times in peoples lives as well. People became more mobile. Cars extended the range of dating as well as enabled back-seat sexual exploration.
In the mid-twentieth century, the advent of things to know about dating a mexican man control as well as safer procedures for abortion changed the equation considerably, and there was less pressure to marry as a means for satisfying sexual urges.
The alkali which leaches out is neutralized by the acid and fewer hydroxyl ions are available to react with the silica. This causes the silica layer to thicken and become gelatinized as the alkali leaches out. Glass excavated from an alkaline environment is less likely to have laminated layers because there is an abundance of hydroxyl ions to react with the silica network. Normally a protective layer does not form on glass exposed to alkaline solutions.
The dissolution of the glass proceeds at a constant rate. The alkali ions are always extracted in excess of the silica, leaving an alkali deficient layer which continually thickens as the deterioration moves deeper into the glass. There are considerable differences of opinion as to what to do with unstable glass. Some advise that the only treatment should be to keep the glass in low relative humidities so the glass does not have any moisture to react with.