sorry: It does NOT say
that is when the NC went into effect:
(that is your personal interpretation not taught by your Church)
but this does:
15 Therefore he is the mediator of a new covenant, (diathéké) so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant.
16 For where a will (diathéké) is involved, the death of the one who made it must be established.
17For a will (diathéké) takes effect ONLY at death, since it is not in force as long as the one who made it is alive."
and so does this:
From The Vatican website (the numbers 13 and 14 are links)
[15-22] Jesus' role as mediator of the new covenant is based upon his sacrificial death
Hebrews 8:6). His death has effected
deliverance from transgressions, i.e., deliverance from sins committed under the old covenant, which the Mosaic sacrifices were incapable of effacing. Until this happened, the eternal inheritance promised by God could not be obtained (⇒
Hebrews 9:15). This effect of his work follows the human pattern by which a last will and testament becomes effective only with the death of the testator
Hebrews 9:16-17). The Mosaic covenant was also associated with death, for Moses made use of blood to seal the pact between God and the people (⇒
Hebrews 9:18-21). In Old Testament tradition, guilt could normally not be remitted without the use of blood (⇒
Hebrews 9:22; cf ⇒
[16-17] A will . . . death of the testator: the same Greek word diatheke, meaning "covenant" in ⇒
Hebrews 9:15, ⇒
18, is used here with the meaning will.
The new covenant, unlike the old, is at the same time a will that requires the death of the testator. Jesus as eternal Son is the one who established the new covenant together with his Father, author of both covenants;
at the same time he is the testator whose death puts his will into effect."
Let's see if you can be corrected