Yesterday.
For example, consider the following actual law:
This is an example of a reasonable age of consent law, and we really ought to question the motives of anyone over 20 who thinks that such a law is too strict. Same goes for New Hampshire's more nuanced law, which also has an age of consent of 16, a four-year close-in-age exemption, and a hard minimum age of 13.
Think about it.
As for those who believe the age of consent should be raised to (or remain) 18 in a given state, one could simply adopt the same aforementioned law as written above, and add to it the following section or something similar:
(3) The person, being eighteen (18) years old or more, engages in sexual intercourse or sexual intrusion with another person who is less than eighteen (18) years old and who is at least five years younger than the defendant, and is not married to the defendant.
And that would resolve essentially all of the problems associated with current age-of-consent laws even if as high as 18. Unfortunately, not every state even has close-in-age exemptions at all, and some of those laws, such as California, effectively criminalize both parties if they are both under 18. Such a thing is an absolute travesty, in dire need of reform. Ditto for any other laws that are written too broadly or vaguely or that give judges way too much discretion as well.
And come to think of it, any marriage exemptions to such laws should also be removed, since that implies marriage below the age of consent is permissible. And in many states it is, provided there is parental and/or judicial consent. But what it really is in practice is a loophole to cover up abuse and coercion. That said, existing marriages involving 16-17 year olds could be "grandfathered" as "valid but voidable" while the new laws only apply going forward.
As for commerical sex work, "survival sex", and cases where the older person is in a direct position of authority over the younger person, an addtional section can (and should) be added that sets the age limit higher than it would otherwise be (i.e. 18 rather than 16) and zero tolerance in regards to age gaps. But these examples are the exceptions, and no reason for the general age of consent to be affected by such exceptions. And we can also have graduated and enhanced penalties for very large age gaps (i.e. over 21 and under 14, over 18 and under 13, etc.) as well.
One good article about age of consent issues can be found here, written by the ever-insightful Thomas Macaulay Miller of Yes Means Yes. As he notes, it really should not be seen as a particularly radical position that a 40 year old should not be having sex with a 13 year old, period, no matter how much the younger person appears to "invite" such conduct. Sometimes we really need a hard, bright line even if it seems a bit arbitrary. At the same time, not having a close-in-age exemption ends up hurting the very same young people that such laws are supposed to protect.
Oh, and another thing. The idea that a 17 year old sending a nude photo of him or herself to another 17 year old can be charged with "child pornography" under federal law and given a mandatory minimum sentence of 15 years in adult prison is absolutely unconsionable. Let that sink in. And such a travesty is a sign that our country has gone completely insane.
Meanwhile, the real rapists and child molesters are out there flying under the radar, and are often hiding in plain sight right now as we speak. Seriously.
Food for thought.