When we analyze the original Japanese for "Promised Time"--"shun-kokugen"--the following usages can be found in the dictionary:
shun---(1) the season or time when certain fish, vegetables, or fruits are considered to be at their peak flavor (2) the most appropriate time to do a certain task or activity
kokugen---(1) a predetermined or appointed time (2) time or moment
These two words are combined to create "Promised Time," a phrase that has a highly significant and special meaning in Tenrikyo.
At the beginning when God the Parent set about to create the world and humanity, God saw a fish and serpent in the muddy ocean and, upon discerning their single-heartedness, decided to make them the models of husband and wife. God the Parent then made the following promise to have them agree to participate in God's creation: "When the years equal to the number of [your] first-born [elapse, you will] be returned to the Residence of Origin, the place of original conception, and [will] be adored by [your] posterity" (refer to "Truth of Origin" [5.63] and "Ten Aspects of the Complete Providence" [5.62]). We are taught that after the other instruments were determined, nine hundred million, ninety-nine thousand, nine hundred and ninety-nine children were conceived in the womb of Izanami-no-Mikoto. Consequently, "the years equal to the number of the first-born" means nine hundred million, ninety-nine thousand, nine hundred and ninety-nine years. This is the amount of time that passed before God the Parent's promise could be fulfilled. But before this, Oyasama, who possessed the soul of Izanami-no-Mikoto, the mother at human creation, was born into the world and brought back by God the Parent to the Residence of Origin, the place of original conception, when She married into the Nakayama family. God the Parent's promise at creation was finally fulfilled on October 26, 1838, when the path began with Oyasama being settled as the Shrine of Tsukihi. We call this moment the "arrival of the Promised Time" (shun-kokugen no torai).
The number nine hundred million, ninety-nine thousand, nine hundred and ninety-nine is not only a number approaching one billion, but is also a number that has profound significance. If we were to render this number (in Japanese, kuoku kuman kusen kuhyaku kuju-ku) into the classical Japanese numerical system, it becomes 999,999, a number that is a succession of nines and one short of becoming a full or complete number.
From this we can come to understand that humanity becomes complete with the addition of Oyasama, our true and original mother. The day marking the passage of nine hundred million, ninety-nine thousand, nine hundred and ninety-nine years--namely October 26, 1838--symbolizes the beginning of a new age. It marks an unchangeable and absolute moment in time when the ultimate teaching began, the teaching that aims to bring about the reconstruction of the world into the world of the Joyous Life.
Thus we use the term "Promised Time" to refer to the heavily significant and irreplaceable moment in time made possible by God the Parent's intention while conveying the absolute nature of the day of origin when the Teaching was founded. Further, the words "shun" (rendered in English as "season," "time," or "seasonable time") and "kokugen" ("appointed" or "fixed time") are both used to refer to extremely significant moments in each of our lives that are most timely according to God the Parent's profound intention.